A role for vitamin D and the vitamin D receptor in keloid disorder

Keloids are disfiguring fibroproliferative lesions that can occur in susceptible individuals following any skin injury. They are extremely challenging to treat, with relatively low response rates to current therapies and high rates of recurrence after treatment. Although several distinct genetic loci have been associated with keloid formation in different populations, there has been no single causative gene yet identified and the molecular mechanisms guiding keloid development are incompletely understood. Further, although it is well known that keloids are more commonly observed in populations with dark skin pigmentation, the basis for increased keloid risk in skin of colour is not yet known. Because individuals with dark skin pigmentation are at higher risk for vitamin D deficiency, the role of vitamin D in keloid pathology has gained interest in the keloid research community. A limited number of studies have found lower serum vitamin D levels in patients with keloids, and reduced expression of the vitamin D receptor (VDR) in keloid lesions compared with uninjured skin. Vitamin D has documented anti-inflammatory, anti-proliferative and pro-differentiation activities, suggesting it may have a therapeutic role in suppression of keloid fibrosis. Here we review the evidence supporting a role for vitamin D and VDR in keloid pathology.     

Hereditary vitamin D–resistant rickets (HVDRR) owing to a heterozygous mutation in the vitamin D receptor

Hereditary vitamin D–resistant rickets (HVDRR) is a rare autosomal recessive disease caused by mutations in the vitamin D receptor (VDR). Patients exhibit severe rickets and hypocalcemia. Heterozygous parents and siblings appear normal and exhibit no symptoms of the disease. We analyzed the VDR gene of a young girl who exhibited the clinical features of HVDRR without alopecia. The patient had clinical and radiographic features of rickets, hypocalcemia, and elevated serum concentrations of 1,25‐dihydroxyvitamin D [1,25(OH)₂D]. A single heterozygous missense mutation was found in the VDR gene that substituted glutamic acid with alanine at amino acid 420 (E420A). Sequencing of the girl's VDR cDNAs showed that the f/M1 allele contained the E420A mutation, whereas the F/M4 allele was completely normal. The girl's father, who was also heterozygous for the E420A mutation on the f/M1 allele, exhibited minor symptoms of vitamin D resistance. In contrast, the mother had no signs of the disease and had no mutations in her VDR gene. Both the girl and the father's skin fibroblasts showed resistance to 1,25(OH)₂D₃ by their severely reduced induction of CYP24A1 gene expression. In transactivation assays, the E420A mutant VDR showed dominant‐negative activity towards the wild‐type VDR. This is the first report that we are aware of describing a patient with HVDRR caused by a single heterozygous missense mutation in the VDR gene. The E420A mutant appears to act in a dominant‐negative fashion, silencing the wild‐type VDR and resulting in an attenuated response to 1,25(OH)₂D₃. © 2011 American Society for Bone and Mineral Research     

Compound Heterozygous Mutations in the Vitamin D Receptor in a Patient With Hereditary 1,25‐Dihydroxyvitamin D‐Resistant Rickets With Alopecia

Hereditary vitamin D‐resistant rickets (HVDRR) is a rare recessive genetic disorder caused by mutations in the vitamin D receptor (VDR). In this study, we examined the VDR in a young girl with clinical features of HVDRR including rickets, hypophosphatemia, and elevated serum 1,25(OH)₂D. The girl also had total alopecia. Two mutations were found in the VDR gene: a nonsense mutation (R30X) in the DNA‐binding domain and a unique 3‐bp in‐frame deletion in exon 6 that deleted the codon for lysine at amino acid 246 (ΔK246). The child and her mother were both heterozygous for the 3‐bp deletion, whereas the child and her father were both heterozygous for the R30X mutation. Fibroblasts from the patient were unresponsive to 1,25(OH)₂D₃ as shown by their failure to induce CYP24A1 gene expression, a marker of 1,25(OH)₂D₃ responsiveness. [³H]1,25(OH)₂D₃ binding and immunoblot analysis showed that the patient's cells expressed the VDRΔK246 mutant protein; however, the amount of VDRΔK246 mutant protein was significantly reduced compared with wildtype controls. In transactivation assays, the recreated VDRΔK246 mutant was unresponsive to 1,25(OH)₂D₃. The ΔK246 mutation abolished heterodimerization of the mutant VDR with RXRα and binding to the coactivators DRIP205 and SRC‐1. However, the ΔK246 mutation did not affect the interaction of the mutant VDR with the corepressor Hairless (HR). In summary, we describe a patient with compound heterozygous mutations in the VDR that results in HVDRR with alopecia. The R30X mutation truncates the VDR, whereas the ΔK246 mutation prevents heterodimerization with RXR and disrupts coactivator interactions.     

Attenuated up-regulation of vitamin D-dependent calcium-binding proteins by 22-oxa-1,25-dihydroxyvitamin D3 in uremic rats: A possible mechanism for less-calcemic action

SUMMARY: 22-Oxa-1,25-dihydroxyvitamin D₃ (OCT) is an analogue of vitamin D with less calcemic action than 1,25-dihydroxyvitamin D₃ (1,25D3), and thus may be advantageous in the treatment of secondary hyperparathyroidism in dialysis patients. to further elucidate the mechanisms of less-calcemic action of OCT in chronic renal failure, we examined the effects of OCT and 1,25D3 on mRNA levels for vitamin D-dependent 9-KDa calcium binding protein (CaBP-D_9K) in the intestinal mucosa and 28-KDa (CaBP-D_28K) in the kidney. In Sprague-Dawley rats made uremic by 5/6 nephrectomy for three months, OCT at doses of 0.25, 1.25 and 6.25 μg/kg, or 1,25D3 at 0.025,0.125 and 0.625 μg/kg were administered intravenously three times per week for two weeks. At 24 h after the final injection, enhanced serum PTH and PTH mRNA levels were successfully suppressed both by OCT and 1,25D3 in a dose dependent manner. However, OCT induced less hypercalcemia than 1,25D3. 1,25D3 markedly upregulated the expression of CaBP-D_9K and CaBP-D_28K genes, while they were not affected by OCT at all. In conclusion, such attenuated effects of OCT on calcium-binding proteins may play a role in the noncalcemic action, because number of CaBP-D_9K has been suggested to correlate with calcium absorption in the intestine.     

Novel nonsecosteroidal vitamin D receptor modulator inhibits the growth of LNCaP xenograft tumors in athymic mice without increased serum calcium.

BACKGROUND: We recently reported on novel vitamin D receptor (VDR) modulators that are structurally distinct from the secosteroid 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), the endogenous activator of VDR. One of these compounds, LG190119, was tested for the ability to inhibit the growth of LNCaP human prostate cancer cell-derived tumors in athymic mice. METHODS: In one study, athymic mice with established LNCaP xenograft tumors were dosed orally every day with LG190119 (3 or 10 mg/kg) or with a synthetic analog of 1,25(OH)(2)D(3), EB1089 (1 microg/kg), for 15 days. In another study ("prevention mode"), oral administration (every other day) of 10 mg/kg LG190119 or a non-hypercalcemic dose of 1,25(OH)(2)D(3) (0.5 microg/kg) was initiated prior to tumor development and continued for 84 days. In both studies, tumor volumes, mouse weights, and serum calcium levels were measured. RESULTS: In the established tumor study, LG190119 at each dose resulted in significant tumor growth inhibition without hypercalcemia at both 10 and 15 days. EB1089 treatment resulted in significant tumor growth inhibition only at Day 10 and resulted in hypercalcemia at Day 15. In the prevention-mode study, LG190119 markedly slowed tumor growth without increased serum calcium in comparison with either vehicle or 1,25(OH)(2)D(3) treatment (P < 0.001). CONCLUSIONS: LG190119 effectively inhibited LNCaP xenograft tumor growth without increased serum calcium levels or any other apparent side effects. Compounds of this class may represent promising new therapeutics for treatment of prostate cancer and other cancers with fewer undesirable side effects than currently used drugs.     

Serum vitamin D metabolites and nuclear uptake of (3H)-1,25-dihydroxyvitamin D3 in monocytes from patients with autosomal dominant osteopetrosis: a study of two radiological types

The nuclear uptake of (³H)-1,25 dihydroxyvitamin D₃ in freshly isolated human monocytes and the serum levels of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were investigated in 13 patients with autosomal dominant osteopetrosis and in sex- and age-matched controls. Seven patients had type I osteopetrosis characterized by diffuse, symmetrical osteosclerosis with pronounced sclerosis of the skull and increased thickness of the cranial vault. The other six patients had type II with “Rugger Jersey Spine” and “endobones” as characteristic findings. In type I osteopetrosis the serum 1,25-dihydroxy vitamin D was significantly reduced (p < 0.05), whereas serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D receptor binding were normal. In type II osteopetrosis the serum vitamin D metabolites were normal, as was the maximal binding capacity (Bmax) of 1,25-dihydroxyvitamin D to the nuclear receptor. The dissociation constant (Kd), however, was significantly increased (p < 0.01) indicating a modest resistance to 1,25-dihydroxyvitamin D. It is concluded that a general end-organ resistance to 1,25-dihydroxyvitamin D at the receptor level does not exist in type I osteopetrosis, but may contribute to some of the radiological and biochemical findings in type II.     

Serum vitamin D metabolites and nuclear uptake of (H)-1,25-dihydroxyvitamin D3 in monocytes from patients with autosomal dominant osteopetrosis: A study of two radiological types

The nuclear uptake of (³H)-1,25 dihydroxyvitamin D₃ in freshly isolated human monocytes and the serum levels of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were investigated in 13 patients with autosomal dominant osteopetrosis and in sex- and age-matched controls. Seven patients had type I osteopetrosis characterized by diffuse, symmetrical osteosclerosis with pronounced sclerosis of the skull and increased thickness of the cranial vault. The other six patients had type II with “Rugger Jersey Spine” and “endobones” as characteristic findings. In type I osteopetrosis the serum 1,25-dihydroxy vitamin D was significantly reduced (p < 0.05), whereas serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D receptor binding were normal. In type II osteopetrosis the serum vitamin D metabolites were normal, as was the maximal binding capacity (Bmax) of 1,25-dihydroxyvitamin D to the nuclear receptor. The dissociation constant (Kd), however, was significantly increased (p < 0.01) indicating a modest resistance to 1,25-dihydroxyvitamin D. It is concluded that a general end-organ resistance to 1,25-dihydroxyvitamin D at the receptor level does not exist in type I osteopetrosis, but may contribute to some of the radiological and biochemical findings in type II.     

A novel E153X point mutation in the androgen receptor gene in a patient with complete androgen insensitivity syndrome

Aim: To study a 46, XY newborn patient with a phenotype suggestive of an androgen insensitivity syndrome toconfirn an anomaly in the AR gene. Methods: Genomic DNA from leukocytes was isolated in order to analyze SRYgene by PCR and sequencing of the eight exons of AR gene. Isolation of human Leydig cell mesenchymal precursorsfrom the testis was performed in order to study testosterone production and response to hCG stimulation in culture.Results: Surgical exploration disclosed two testes, no Wolffian structures and important Mullerian derivatives. TheSRY gene was present in peripheral blood leukocytes. Sequencing of the AR gene evidenced a previously unreported Gto T transversion in exon 1 that changed the normal glutamine 153 codon to a stop codon. Interstitial cell culturesproduced sizable amounts of testosterone and were responsive to hCG stimulation. Conclusion: This E153X nonsensepoint mutation has not been described previously in cases of AIS, and could lead to the synthesis of a short truncated(15     

A new point mutation of the androgen receptor gene in a patient with partial androgen resistance and severe oligozoospermia

Mutations of the androgen receptor gene in genetic males cause a variety of androgen insensitivity syndromes varying from female phenotype through intersexuality to male phenotype with infertility. The identification of a missense mutation in the steroid-binding domain in an infertile male with mild features of androgen insensitivity is reported here.     

The Glu228Ala polymorphism in the ligand binding domain of death receptor 4 is associated with increased risk for prostate cancer metastases.

BACKGROUND: Death receptor 4, encoded by the TNFRSF10A gene, is an important mediator of apoptosis and its dysfunction may be related to cancer development and distant tumor spread. A single nucleotide polymorphism in TNFRSF10A (Glu228Ala, rs20576) within a conserved region of the extracellular cysteine-rich domain of death receptor 4 has been associated with an increased risk for a variety of tumor entities. Aim of the present study was to evaluate the role of the TNFRSF10A polymorphism in metastatic progression of prostate cancer after radiation therapy. METHODS: We carried out a prospective study including 702 prostate cancer patients from the Austrian PROCAGENE (Prostate Cancer Genetics) study. Development of metastases was examined in regular follow-up investigations. TNFRSF10A genotypes were determined by a 5'-nuclease assay (TaqMan). RESULTS: Within a median follow-up time of 10 months (range 0-60 months), 24 (3.4%) patients developed metastases. In a Cox regression model including age at diagnosis and risk group as potential confounders, carriage of an 228Ala allele was associated with a relative risk of 2.47 (95% CI 1.10-5.54; P=0.028) for metastases. TNFRSF10A genotypes were not associated with tumor stage, grade, risk group or age at diagnosis. CONCLUSION: We conclude that the TNFRSF10A Glu228Ala polymorphism may be a novel independent risk factor for prostate cancer metastases after radiation therapy.     

BsmI vitamin D receptor genotypes influence the efficacy of antiresorptive treatments in postmenopausal osteoporotic women. A 1-year multicenter, randomized and controlled trial

Vitamin D receptor (VDR) gene polymorphisms could be considered one of the factors influencing the efficacy of the anti-osteoporotic treatments. In this multicenter, prospective, randomized and controlled trial we evaluated whether BsmI vitamin D receptor (VDR) genotypes influence the efficacy of antiresorptive treatment regimes (administered alone or in combination) in postmenopausal osteoporotic women. Using restriction endonuclease, we identified the BsmI VDR polymorphism in 1,100 postmenopausal women with osteoporosis. The women were randomized, taking account of genotype, into five treatment groups: (1) alendronate (Aln, 10 mg/day) plus raloxifene (Rlx, 60 mg/day); (2) Aln plus hormone replacement therapy (HRT, 0.625 mg/day conjugated equine estrogens plus 2.5 mg/day medroxyprogesterone acetate); (3) Aln alone; (4) HRT alone; and (5) Rlx alone. Lumbar-spine bone mineral density (BMD) and bone turnover markers were measured at study entry and after 1 year of treatment. Using the general linear model (GLM) repeated-measures procedure, the means of BMD and bone turnover markers significantly differed from baseline after a period of treatment. In particular, the mean change from baseline for BMD was –0.034 (95% confidence interval [CI]: –0.037 to –0.031, P <0.001); for serum osteocalcin (OC) it was 1.369 (95% CI: 1.289 to 1.448, P <0.001); and for urinary deoxypyridinoline (DPD) it was 1.322 (95% CI: 1.242 to 1.401, P <0.001), indicating a considerable variation before and after treatment of these indicators. In all three cases these effects appeared significantly influenced by treatments, genotypes, and the treatments*genotypes interaction term (P <0.001 each, except for the BMD and genotype effect with P =0.02), and not by the investigational centers involved in the study. In conclusion, in postmenopausal osteoporotic women, BsmI VDR genotypes influence the efficacy of antiresorptive drugs particularly when used in combination.