Vitamin D receptor polymorphisms in immune thrombocytopenic purpura

The impact of genetic variants related to vitamin D and autoimmunity: A systematic review

Over the past few years, there has been a notable increment in scientific literature aimed at unraveling the genetic foundations of vitamin D signaling and its implications for susceptibility to autoimmunity, however, most of them address isolated diseases. Here, we conducted a systematic review of genetic variants related to vitamin D and autoimmune diseases and we discussed the current landscape of susceptibility and outcomes. Of 65 studies analyzed, most variants cited are in vitamin D binding protein (VDBP; rs2282679 GC gene), 25-hydroxylase (rs10751657 CYP2R1), 1α-hydroxylase (rs10877012, CYP27B1) and the nuclear hormone receptor superfamily [FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232), and TaqI (rs731236) in VDR gene]. Therefore, our findings confirmed the associations of several genetic variants of vitamin D signaling with a broad spectrum of autoimmune diseases/traits. In addition, given the low number of papers found with functional analysis, further studies to elucidate the real effect that the variants exert on Vitamin D signaling are recommended.

Vitamin D Receptor Gene Polymorphisms in Childhood Brucellosis in Turkish Children

Objective The vitamin D receptor gene (VDR) polymorphisms and the risk of various infections have been studied. An association with brucellosis and vitamin D levels has been investigated but not yet with VDR gene polymorphisms. We aimed to examine the association between VDR gene polymorphisms and susceptibility to childhood brucellosis.

Methods This case–control study included patients with brucellosis and healthy controls. After extracting genomic DNA using a Qiagen blood DNA isolation kit, five VDR single nucleotide polymorphisms (SNPs), including Cdx-2, FokI, BsmI, ApaI, and TaqI gene, were amplified. Genetic distribution of these SNPs of VDR gene in patient and control groups were compared.

Results A total of 38 patients with brucellosis and 89 healthy controls were evaluated. The genotype distribution of Cdx2, FokI, BsmI, and ApaI polymorphisms were similar between patients and healthy controls. However, the CC homozygous genotype for VDR gene TaqI was significantly overexpressed in patients compared with controls (23.7 vs. 7.9%; p = 0.042). The frequency of the C allele of the TaqI genotype was significantly different between patients and controls (p = 0.018). On the other hand, presence of the A allele in the BsmI was associated considerably with an increased risk of brucellosis (p = 0.037). VDR polymorphism distribution was similar according to age, presence of complicated disease, and presence of bacteremia. The heterozygote TaqI polymorphism was more common in patients presented as subacute and chronic symptoms (p = 0.036).

Conclusion Our results indicated the possible role in TaqI polymorphism of the VDR gene for the risk of brucellosis at the time of exposure to infection.

Vitamin D changes expression of DNA repair genes in the patients with multiple sclerosis

Oxidative stress (OS) plays an essential role in demyelination and tissue injury related to pathogenesis of multiple sclerosis (MS). On the other hand, vitamin D (VD) as an antioxidant reduces oxidative stress and has been used as adjuvant therapy in autoimmune diseases. Although VD supplementation is suggested as a protective and immunomodulation factor for MS patients, the molecular mechanisms remain unclear. Given that VD may modulate the immune system of MS patients through the DNA repair pathway, we aimed to evaluate the effects of VD supplementation in DNA repair genes expression including OGG1, MYH, MTH1, and ITPA. Transcript levels were measured using the RT-qPCR method in peripheral blood mononuclear cells (PBMCs) of relapsing-remitting multiple sclerosis (RRMS) patients before and after two months of VD supplementation. Furthermore, in silico analysis and correlation gene expression analysis was performed to find the biological binding sites and the effect of NRF2 on the regulation of DNA repair genes. Our data revealed that in MS patients, 2-month VD treatment significantly altered the expression of MYH, OGG1, MTH1, and NRF2 genes. A significant correlation was observed between DNA repair genes and NRF2 expression, which was confirmed by the presence of antioxidant response element (ARE) binding sites in the promoter of OGG1, MYH, and MTH1 genes. This study demonstrated that the impact of VD on MS patients may be mediated through the improvement of DNA repair system efficiency. This finding brought some new evidence for the involvement of DNA repair genes in the physiopathology of MS patients.

Vitamin D Insufficiency is Not Associated With Pediatric and Adolescent Immune Thrombocytopenia: A Study in Conjunction With its Receptor Genetic Polymorphisms

Idiopathic thrombocytopenic purpura (ITP) is a heterogeneous immunologic disorder. Vitamin D has immune-modulatory effects. The pleiotropic effects of vitamin D are exerted via vitamin D receptor (VDR) and its genetic alterations could influence its functions. In our study, we measured the serum 25-hydroxyvitamin D levels in 98 Pediatric and Adolescent ITP patients, in addition to 100 apparently healthy controls. Genetic polymorphisms of the VDR gene FokI, BsmI, ApaI, and TaqI were tested using specific restriction enzymes for each polymorphism. Vitamin D deficiency in the studied Pediatric age was a dominant factor, but it was found not to be associated with Pediatric ITP. However, patients carrying the FokI CC genotype had statistically higher vitamin D levels compared with those carrying other genotypes (P=0.036). Patients who were carriers of the BsmI G allele had a nearly 2-fold higher risk of ITP (odds ratio: 2.203; 95% confidence interval: 1.467-3.309). Therefore, the BsmI polymorphism of VDR could be considered a molecular risk factor for ITP.

Serum Vitamin D Levels in Children with Immune Thrombocytopenia

OBJECTIVE

Immune thrombocytopenia (ITP) is an acquired immuno-mediated disorder characterized by thrombocytopenia with an increased risk of bleeding. In recent years 1,25[OH]2D3 has been rediscovered as an immune modulator. We decided to evaluate serum Vitamin D levels in a cohort of children with immune thrombocytopenia in order to discover if Vitamin D concentrations may predict ITP duration.

METHODS

Thirty children were enrolled in this study (sixteen with chronic ITP and fourteen with newly diagnosed ITP) to assess serum Vitamin D levels.

RESULTS

The results showed that 80% of the enrolled children presented a D hypovitaminosis status. Children with newly diagnosis ITP showed no statistically significantly higher median values of Vitamin D compared to chronic ITP.

CONCLUSION

This study may suggest that Vitamin D deficiency does not represent a chronicity factor for ITP. However, further studies are needed to understand the role of Vitamin D in ITP pathogenesis.

Association Between Vitamin D Receptor Gene Polymorphism rs2228570 and Allergic Rhinitis

Background

Vitamin D receptor (VDR) gene polymorphisms are involved in a variety of immune-related diseases, and VDR is associated with allergic rhinitis. The present study explored the associations between VDR gene polymorphisms and allergic rhinitis in the Chinese population.

Methods

The study population consisted of 400 patients with allergic rhinitis and 400 healthy controls. General characteristics were determined by interview. Blood DNA was extracted and genotyping was performed via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The associations of each genetic variant with risk for AR were assessed by calculating the odds ratio (OR) with 95% confidence interval (95% CI).

Results

No significant differences were observed in general characteristics between cases and controls. The distributions of genotypes at the rs2228570 locus of the VDR gene conformed to Hardy–Weinberg equilibrium. There was a significant difference in the distribution of rs2228570 genotype (P<0.001) between cases and controls. Compared to GG and GA genotypes, the AA genotype increased the risk of AR (OR=3.27, 95% CI: 2.10–5.11, P=0.000; OR=2.58, 95% CI:1.63–4.08, P<0.001). Similar results were also observed in the dominant model (OR=1.64, 95% CI:1.24–2.17, P<0.001) and codominant model (OR=2.95, 95% CI:1.93–4.51, P<0.001). The A allele was still associated with elevated risk gene for AR after adjusting for potential confounding factors. Subgroup analyses indicated an interaction between alcohol and rs2228570 in the risk of allergic rhinitis. The A allele also increased the risk for AR in the population without asthma (OR=1.85, 95% CI:1.46–2.34, P<0.001).

Conclusion

VDR gene polymorphism is associated with AR, and the AA genotype of rs2228570 is associated with the increased risk of AR in the Chinese population.

The Role of IL-6, TNF-α, and VDR in Inhibiting the Growth of Salmonella Typhi: in vivo Study

Background and aim:

The prevalence of typhoid fever is reportedly high, especially in Asia. When a pathogen enters the human body, there are markers in the form of molecules that will be known by the innate immune system. Specific molecular markers of gram negative bacteria, which are Lipopolysaccharides (LPS) and Toll-Like receptors-4 will interact with LPS. The binding between LPS and TLR-4 will give rise to activation signals that will activate innate immune cells. Immune cells will release a number of proinflammatory cytokines, such as TNF-α, IL-1, and IL-6. While Vitamin D Receptors (VDR) are expressed in large amounts in tumor tissue and infected cells. This study aimed to prove the role of IL-6, TNF-α, and VDR in inhibiting bacterial growth in mice that have been induced by S.Typhi.

Methods:

This research was a real experimental pre-post test design to investigate the level of IL-6, TNF-α and VDR in suppressing the growth of bacteria in the peritoneal fluid of S. Typhi, male, mice BALB/c. Mice were divided into three groups comprised of 10 mice each. All mice in groups A and B were intraperitoneally inoculated with S. Typhi strain Thy1 in study day 0. Group A was treated with antibiotic Levofloxacine, on study day 4th. Another study group, group B, was used as a placebo and received aquades on study day 4th. While group C as a control was not inoculated with S. Typhi. Blood samples from three groups for the calculation of serum Il-6, TNF-α, and VDR were collected. This examination was taken four times; at baseline, 4th day, 10th day, and 30th day. For the calculation of bacterial colony, peritoneal fluid retrieval was collected three times, which is on 4th day, 10th day, and 30th day.

Results:

A repeated measure ANOVA in group A (antibiotic) and group B (placebo) group showed that mean IL-6, TNF-α, and VDR level differed statistically significant between times (p-value 0.000). There was a strong negative correlation between bacterial colony count and VDR level, which was statistically significant in both groups (group A; r = -0.875, p-value = 0.000 vs group B; r = -0.470, p-value = 0.002). IL-6 and TNF-α didn't give significant statistical correlation with bacterial colony count.

Conclusion:

VDR, IL-6, and TNF-α play an important role in killing bacteria. From the results of this study, IL-6 level is related to the number of bacterial colonies, the lower the IL-6 level, the less the number of bacterial colonies. Similarly, TNF-α levels have a positive correlation with the number of bacterial colonies. While VDR levels are also related to the number of bacterial colonies, the higher the VDR level, the lower the number of bacterial colonies.

Hypovitaminosis D Influences the Clinical Presentation of Immune Thrombocytopenia in Children with Newly Diagnosed Disease

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by isolated thrombocytopenia defined as platelet count in peripheral blood <100 × 10⁹/L. Hypovitaminosis D is very common in children with autoimmune diseases. To analyze whether hypovitaminosis D is associated with the clinical presentation of ITP in children, medical records of 45 pediatric patients with newly diagnosed immune thrombocytopenia in the coastal region of Croatia were evaluated. The severity of bleeding was assessed using two bleeding scores. Children with lower 25-hydroxyvitamin D (25(OH)D) values had higher values of the skin-mucosa-organ-gradation (SMOG) bleeding score and respectively more severe bleeding on diagnosis of ITP. With further analysis of the main domains of that score, we found that patients with a lower 25(OH)D value had more severe bleeding in the skin and organs. When 25(OH)D and ITP Bleeding Scale (IBLS) score were analyzed, a negative correlation was found, but it was not significant. Our findings suggest that hypovitaminosis D influences the severity of the clinical presentation of ITP in children on initial diagnosis of the disease. Therefore, therapy with 25(OH)D could be a new potential option for treatment of ITP. To investigate the connection between 25(OH)D and the incidence and severity of ITP, further studies, especially randomized controlled studies, are needed.

Cdx-2 polymorphism in the vitamin D receptor gene (VDR) marks VDR expression in monocyte/macrophages through VDR promoter methylation

Caudal-type homeobox protein 2 (CDX-2) is an intestine-specific transcription factor (TF), with a polymorphic binding site (Cdx-2, rs11568820, A/G) in the vitamin D receptor gene (VDR). The molecular mechanism underlying Cdx-2 association with conditions like osteoporosis, which depends on intestinal VDR expression and calcium absorption, is believed to be due to higher affinity of CDX-2 for the ancestral A allele compared to the G allele. However, it is unclear why the polymorphism is associated with diseases like tuberculosis, which is dependent on VDR expression in immune cells that do not express CDX-2. This study aimed to explain Cdx-2 variant association with immune-related conditions. We hypothesised that the effect of Cdx-2 polymorphism on VDR expression in monocytes/macrophages, devoid of the CDX-2 TF, is indirect and dependent on circulating 25(OH)D₃ and VDR methylation. Primary monocyte/macrophages from healthy donors (n = 100) were activated though TLR2/1 elicitation. VDR mRNA and 25(OH)D₃ were quantified by RT-qPCR and LC-MS/MS, respectively. Genotyping and methylation analysis were done by pyrosequencing. AA vs. AG/GG showed reduced levels of 25(OH)D₃ (P < 0.010), higher VDR promoter methylation (P < 0.050) and lower VDR mRNA induction (P < 0.050). Analysis of covariance confirmed that the effect of Cdx-2 variants depends primarily on VDR methylation. Thus, VDR methylation may confound association studies linking VDR polymorphisms to disease.