Vitamin D-induced up-regulation of human keratinocyte cathelicidin anti-microbial peptide expression involves retinoid X receptor alpha

作者：Svensson Daniel; Nebel Daniel; Voss Ulrikke; Ekblad Eva; Nilsson Bengt Olof^*

来源：Cell and Tissue Research, 2016, 366(2): 353-362.

DOI：10.1007/s00441-016-2449-z

• Cathelicidin
• Keratinocyte
• Retinoid X receptor
• Vitamin D
• Vitamin D receptor

The biologically active form of vitamin D, 1 alpha,25-dihydroxyvitamin D3 (1,25D3), has been reported to positively regulate the human cathelicidin anti-microbial peptide (CAMP) gene coding for LL-37, but the mechanisms are not completely understood. We have determined the expression of CAMP, vitamin D receptor (VDR), and the retinoid X receptor (RXR) isoforms in human skin and gingival tissue biopsies and investigated the signaling pathways involved in 1,25D3-induced upregulation of CAMP. Human skin and gingival biopsies exhibited few VDR-immunoreactive cells within the stratum basale, whereas rat colon enterocytes (positive control) possessed abundant VDR immunoreactivity. Nuclear VDR immunoreactivity was demonstrated in human skin keratinocytes (HaCaT cells). Gene analysis revealed that human skin biopsies expressed higher levels of both CAMP and RXR alpha mRNA than human gingival biopsies, whereas VDR and RXR beta transcript levels were similar in skin and gingiva. In HaCaT cells, treatment with 1,25D3 (5 nM and 1 mu M) for 4 and 24 h up-regulated CAMP mRNA several fold, and treatment with 1,25D3 for 24 h increased protein expression of the pro-form of LL-37 (hCAP-18) by about 13 times. The 1,25D3-evoked stimulation of HaCaT CAMP expression was associated with attenuated VDR mRNA and protein expression. Treatment with RXR alpha short interfering RNA reversed the 1,25D3-induced CAMP expression in HaCaT cells, showing that RXR alpha is involved in the up-regulation of CAMP by 1,25D3. We conclude that the 1,25D3-evoked stimulation of CAMP expression in human skin keratinocytes is dependent on RXR alpha but is not associated with the up-regulation of VDR expression.

• 出版日期2016-11