Vitamin D₃-Mediated Regulation of the Antimicrobial Peptides CAMP and DEFB4 Is Evolutionarily Important for Innate Immunity in Humans and Primates.

The seco-steroid hormone 1,25(OH)₂D₃ (vitamin D₃) and its analogs induce the expression of cathelicidin antimicrobial peptide (CAMP or CAP18) and human β-defensin 4 (DEFB4, formerly DEFB2) in human bone marrow cells, acute myeloid leukemia cells, monocytes/macrophages, neutrophils, skin, and cell lines from carcinomas of the lung and head and neck. The induction is mediated by a DR3-type vitamin D response element (VDRE) located in the promoter of each gene. We demonstrated the induction of CAMP by vitamin D₃ does not occur in murine cells. The induction appears to be conserved in humans and chimpanzees, but not in other mammals as indicated by the absence of the VDRE in the murine, rat, and canine CAMP and DEFB4 promoters. The VDRE of the CAMP promoter is present in a short-interspersed nuclear element (SINE) of the Alu-Sx subfamily. This class of transposable elements is found throughout primate genomes. In contrast, the DEFB4 VDRE is not located within such an element. We hypothesized that this unique vitamin D3-regulated expression of antimicrobial peptides is evolutionarily conserved in other primates in addition to humans and chimpanzees. To test this, we designed oligonucleotides to highly conserved sequences on either side of the CAMP or DEFB4 VDREs and amplified by PCR the region from genomic DNA of either New World Monkeys (NWM; marmoset) or Old World Anthropoids (OWA; Rhesus macaque &Savanna monkey). Sequence for the orangutan CAMP promoter was obtained from the trace archive at NCBI. Sequencing and analysis of the PCR products revealed that the promoter and VDRE of the DEFB4 and CAMP genes were highly conserved among all the primates. The CAMP gene SINE from human, chimp, orangutan, and Savanna monkey was approximately 550 bp in size; however, the SINE from Rhesus macaque and the marmoset was about 850 bp in size. The size difference was due to an approximately 300 bp of additional sequence that was highly similar to the SINE element and contained the VDRE. The data suggest that the progenitor of both NWM and OWA possessed the 850 bp SINE and that approximately 300 bp was lost in some OWA. Sequencing of addtional NWM and OWA VDREs and functional studies of both the CAMP and DEFB4 VDREs by reporter gene and gel shifts assays are in progress. The CAMP protein hCAP18 is present at significant levels in the plasma. In preliminary studies, at 24 h post-treatment with vitamin D₃ or an analog, hCAP18 levels in the plasma increased in one normal volunteer and in 4/10 patients on chronic hemodialysis (increase ranged from 25–200%). The levels dropped back down to pretreatment levels by 48 and 72 h post-treatment in the patients. The data suggest that vitamin D₃-mediated regulation of the antimicrobial peptides CAMP and DEFB4 is evolutionarily important for innate immunity in humans and other primates as opposed to non-primate mammals.