1,25-Dihydroxyvitamin D3 Suppresses UV-Induced Poly(ADP-Ribose) Levels in Primary Human Keratinocytes, as Detected by a Novel Whole-Cell ELISA.

Photoprotective properties of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to reduce UV-induced DNA damage have been established in several studies. UV-induced DNA damage in skin such as single or double strand breaks is known to initiate several cellular mechanisms including activation of poly(ADP-ribose) (pADPr) polymerase-1 (PARP-1). DNA damage from UV also increases extracellular signal-related kinase (ERK) phosphorylation, which further increases PARP activity. PARP-1 functions by using cellular nicotinamide adenine dinucleotide (NAD+) to synthesise pADPr moieties and attach these to target proteins involved in DNA repair. Excessive PARP-1 activation following cellular stress such as UV irradiation may result in excessive levels of cellular pADPr. This can also have deleterious effects on cellular energy levels due to depletion of NAD+ to suboptimal levels. Since our previous work indicated that 1,25(OH)2D3 reduced UV-induced DNA damage in part through increased repair via increased energy availability, the current study investigated the effect of 1,25(OH)2D3 on UV-induced PARP-1 activity using a novel whole-cell enzyme- linked immunosorbent assay (ELISA) which quantified levels of the enzymatic product of PARP-1, pADPr. This whole cell assay used around 5000 cells per replicate measurement, which represents a 200-400-fold decrease in cell requirement compared to current commercial assays that measure in vitro pADPr levels. Using our assay, we observed that UV exposure significantly increased pADPr levels in human keratinocytes, while 1,25(OH)2D3 significantly reduced levels of UV-induced pADPr in primary human keratinocytes to a similar extent as a known PARP-1 inhibitor, 3-aminobenzamide (3AB). Further, both 1,25(OH)2D3 and 3AB as well as a peptide inhibitor of ERK-phosphorylation significantly reduced DNA damage in UV-exposed keratinocytes. The current findings support the proposal that reduction in pADPr levels may be critical for the function of 1,25(OH)2D3 in skin to reduce UV-induced DNA damage.

[Biosynthesis of calcifediol and calcitriol: a review].

VD3 is a crucial vitamin for human health, as it enhances calcium absorption in the intestines and prevent rickets. Calcifediol (25(OH)VD3) and calcitriol (1α,25(OH)2VD3) are two derivatives of vitamin D3 that play an important role in preventing and treating osteoporosis, as well as regulating human physiological functions. Currently, the production of calcifediol, and calcitriol primarily relies on chemical synthesis, which has disadvantages such as low product yield, numerous by-products, and environmental unfriendliness. Therefore, developing a green, safe, and environmentally friendly biocatalytic synthesis pathway is of utmost importance. This article mainly reviews the biocatalytic synthesis pathways of calcifediol, and calcitriol. The P450 enzymes, including P450 monooxygenases (cytochrome P450 monooxygenases, CYPs) and P450 peroxygenases (unspecific peroxygenases, UPOs), are crucial for the production of calcifediol and calcitriol. The catalytic mechanism of the extensively studied P450 monooxygenases, the selection of suitable redox partners, and the key residues involved in the enzyme's catalytic activity are analyzed. In addition, the review explores H2O2-driven UPOs, including their catalytic mechanism, strategies for high heterologous expression, and in situ regeneration of H2O2. UPOs are regarded as highly promising biocatalysts because they can facilitate reactions without the need for expensive cofactors and redox partners. This review offers insights into the engineering of P450 for the efficient production of vitamin D3 derivatives.

Spatial detection and consequences of nonrenal calcitriol production as assessed by targeted mass spectrometry imaging.

The immune benefits of vitamin D3 supplementation beyond calcium and phosphate maintenance are highly clinically debated. Kidney expression of CYP27B1 is the source of endocrine, circulating 1,25(OH)2D3 (active form of vitamin D) that maintains serum calcium and phosphate. 1,25(OH)2D3 may also be made by the CYP27B1 enzyme in nonrenal cells, like immune cells, in a process driven by cellular availability of 25(OH)D3 and inflammation. Due to the endocrine nature of 1,25(OH)2D3 in circulation, it is difficult to discern between these 2 sources. We recently created a regulatory deletion model of Cyp27b1 (M1/M21-DIKO) where mice have normal inflammatory-regulated Cyp27b1 expression in nonrenal tissues (unlike global Cyp27b1-KO) but no expression within the kidney. Here, utilizing on-tissue chemical derivatization and matrix assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI), we investigated the distribution of 1,25(OH)2D3 and 25(OH)D3 in the kidney, liver, spleen, and thymus. MALDI-MSI demonstrated increased 1,25(OH)2D3 in nonrenal tissues such as the spleen after vitamin D3 supplementation in M1/M21-DIKO mice. Additionally, from this, we found increased Il4 and decreased Tnfa in the spleen after vitamin D3 supplementation. Taken together, these data demonstrate nonrenal production of 1,25(OH)2D3 in vivo and provide a consequence of vitamin D3 supplementation and nonrenal 1,25(OH)2D3 production in cytokine changes.

The Role of Intestinal Cytochrome P450s in Vitamin D Metabolism.

Vitamin D hydroxylation in the liver/kidney results in conversion to its physiologically active form of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. 1,25(OH)2D3 controls gene expression through the nuclear vitamin D receptor (VDR) mainly expressed in intestinal epithelial cells. Cytochrome P450 (CYP) 24A1 is a catabolic enzyme expressed in the kidneys. Interestingly, a recently identified mutation in another CYP enzyme, CYP3A4 (gain-of-function), caused type III vitamin D-dependent rickets. CYP3A are also expressed in the intestine, but their hydroxylation activities towards vitamin D substrates are unknown. We evaluated CYP3A or CYP24A1 activities on vitamin D action in cultured cells. In addition, we examined the expression level and regulation of CYP enzymes in intestines from mice. The expression of CYP3A or CYP24A1 significantly reduced 1,25(OH)2D3-VDRE activity. Moreover, in mice, Cyp24a1 mRNA was significantly induced by 1,25(OH)2D3 in the intestine, but a mature form (approximately 55 kDa protein) was also expressed in mitochondria and induced by 1,25(OH)2D3, and this mitochondrial enzyme appears to hydroxylate 25OHD3 to 24,25(OH)2D3. Thus, CYP3A or CYP24A1 could locally attenuate 25OHD3 or 1,25(OH)2D3 action, and we suggest the small intestine is both a vitamin D target tissue, as well as a newly recognized vitamin D-metabolizing tissue.

4-Hydroxy-1α,25-Dihydroxyvitamin D3: Synthesis and Structure-Function Study.

The active vitamin D metabolites, 25-hydroxyvitamin D3 (25D3) and 1,25-dihydroxyvitamin D3 (1,25D3), are produced by successive hydroxylation steps and play key roles in several cellular processes. However, alternative metabolic pathways exist, and among them, the 4-hydroxylation of 25D3 is a major one. This study aims to investigate the structure-activity relationships of 4-hydroxy derivatives of 1,25D3. Structural analysis indicates that 1,4α,25(OH)3D3 and 1,4ß,25(OH)3D3 maintain the anchoring hydrogen bonds of 1,25D3 and form additional interactions, stabilizing the active conformation of VDR. In addition, 1,4α,25D3 and 1,4ß,25D3 are as potent as 1,25D3 in regulating the expression of VDR target genes in rat intestinal epithelial cells and in the mouse kidney. Moreover, these two 4-hydroxy derivatives promote hypercalcemia in mice at a dose similar to that of the parent compound.

Discordant Health Implications and Molecular Mechanisms of Vitamin D in Clinical and Preclinical Studies of Prostate Cancer: A Critical Appraisal of the Literature Data.

Clinical and preclinical studies have provided conflicting data on the postulated beneficial effects of vitamin D in patients with prostate cancer. In this opinion piece, we discuss reasons for discrepancies between preclinical and clinical vitamin D studies. Different criteria have been used as evidence for the key roles of vitamin D. Clinical studies report integrative cancer outcome criteria such as incidence and mortality in relation to vitamin D status over time. In contrast, preclinical vitamin D studies report molecular and cellular changes resulting from treatment with the biologically active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (calcitriol) in tissues. However, these reported changes in preclinical in vitro studies are often the result of treatment with biologically irrelevant high calcitriol concentrations. In typical experiments, the used calcitriol concentrations exceed the calcitriol concentrations in normal and malignant prostate tissue by 100 to 1000 times. This raises reasonable concerns regarding the postulated biological effects and mechanisms of these preclinical vitamin D approaches in relation to clinical relevance. This is not restricted to prostate cancer, as detailed data regarding the tissue-specific concentrations of vitamin D metabolites are currently lacking. The application of unnaturally high concentrations of calcitriol in preclinical studies appears to be a major reason why the results of preclinical in vitro studies hardly match up with outcomes of vitamin D-related clinical studies. Regarding future studies addressing these concerns, we suggest establishing reference ranges of tissue-specific vitamin D metabolites within various cancer entities, carrying out model studies on human cancer cells and patient-derived organoids with biologically relevant calcitriol concentrations, and lastly improving the design of vitamin D clinical trials where results from preclinical studies guide the protocols and endpoints within these trials.

Role of Calcitriol and Vitamin D Receptor (VDR) Gene Polymorphisms in Alzheimer's Disease.

Alzheimer's disease (AD) is characterized by amyloid beta (Aß) buildup and neuronal degeneration. An association between low serum vitamin D levels and an increased risk of AD has been reported in several epidemiological studies. Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D, and is generated in the kidney and many other tissues/organs, including the brain. It is a steroid hormone that regulates important functions like calcium/phosphorous levels, bone mineralization, and immunomodulation, indicating its broader systemic significance. In addition, calcitriol confers neuroprotection by mitigating oxidative stress and neuroinflammation, promoting the clearance of Aß, myelin formation, neurogenesis, neurotransmission, and autophagy. The receptors to which calcitriol binds (vitamin D receptors; VDRs) to exert its effects are distributed over many organs and tissues, representing other significant roles of calcitriol beyond sustaining bone health. The biological effects of calcitriol are manifested through genomic (classical) and non-genomic actions through different pathways. The first is a slow genomic effect involving nuclear VDR directly affecting gene transcription. The association of AD with VDR gene polymorphisms relies on the changes in vitamin D consumption, which lowers VDR expression, protein stability, and binding affinity. It leads to the altered expression of genes involved in the neuroprotective effects of calcitriol. This review summarizes the neuroprotective mechanism of calcitriol and the role of VDR polymorphisms in AD, and might help develop potential therapeutic strategies and markers for AD in the future.

Differential effects of cholecalciferol and calcitriol on muscle proteolysis and oxidative stress in angiotensin II-induced C2C12 myotube atrophy.

Renin-angiotensin system activation contributes to skeletal muscle atrophy in aging individuals with chronic diseases. We aimed to explore the effects of cholecalciferol (VD3) and calcitriol (1,25VD3) on signaling of muscle proteolysis and oxidative stress in myotubes challenged with angiotensin II (AII). The mouse C2C12 myotubes were assigned to vehicle, AII, AII + VD3, AII + 1,25VD3, and AII + losartan groups. The expression levels of muscle-specific E3 ubiquitin ligase proteins, autophagy-related proteins, and oxidative stress markers were investigated. We demonstrated the diverse effects of VD3 and 1,25VD3 on AII-induced myotube atrophy. The myotube diameter was preserved by treatment with 100 nM VD3 and losartan, while 1 and 10 nM 1,25VD3 increased levels of FoxO3a, MuRF1, and atrogin-1 protein expression in myotubes exposed to AII. Treatment with AII + 10 nM 1,25VD3 resulted in the upregulation of LC3B-II, LC3B-II/LC3B-I, and mature cathepsin L, which are autophagic marker proteins. The p62/SQSTM1 protein was downregulated and vitamin D receptor was upregulated after treatment with AII + 10 nM 1,25VD3. A cellular redox imbalance was observed as AII + 10 nM 1,25VD3-induced reactive oxygen species and NADPH oxidase-2 overproduction, and these changes were associated with an inadequate response of antioxidant superoxide dismutase-1 and catalase proteins. Collectively, these findings provide a translational perspective on the role of vitamin D3 in alleviating muscle atrophy related to high levels of AII.

Cellular responses to silencing of PDIA3 (protein disulphide-isomerase A3): Effects on proliferation, migration, and genes in control of active vitamin D.

The active form of vitamin D, 1,25-dihydroxyvitamin D3, is known to act via VDR (vitamin D receptor), affecting several physiological processes. In addition, PDIA3 (protein disulphide-isomerase A3) has been associated with some of the functions of 1,25-dihydroxyvitamin D3. In the present study we used siRNA-mediated silencing of PDIA3 in osteosarcoma and prostate carcinoma cell lines to examine the role(s) of PDIA3 for 1,25-dihydroxyvitamin D3-dependent responses. PDIA3 silencing affected VDR target genes and significantly altered the 1,25-dihydroxyvitamin D3-dependent induction of CYP24A1, essential for elimination of excess 1,25-dihydroxyvitamin D3. Also, PDIA3 silencing significantly altered migration and proliferation in prostate PC3 cells, independently of 1,25-dihydroxyvitamin D3. 1,25-Dihydroxyvitamin D3 increased thermostability of PDIA3 in cellular thermal shift assay, supporting functional interaction between PDIA3 and 1,25-dihydroxyvitamin D3-dependent pathways. In summary, our data link PDIA3 to 1,25-dihydroxyvitamin D3-mediated signalling, underline and extend its role in proliferation and reveal a novel function in maintenance of 1,25-dihydroxyvitamin D3 levels.

Male Lrp5A214V mice maintain high bone mass during dietary calcium restriction by altering the vitamin D endocrine system.

Environmental factors and genetic variation individually impact bone. However, it is not clear how these factors interact to influence peak bone mass accrual. Here we tested whether genetically programmed high bone formation driven by missense mutations in the Lrp5 gene (Lrp5A214V) altered the sensitivity of mice to an environment of inadequate dietary calcium (Ca) intake. Weanling male Lrp5A214V mice and wildtype littermates (control) were fed AIN-93G diets with 0.125%, 0.25%, 0.5% (reference, basal), or 1% Ca from weaning until 12 weeks of age (ie, during bone growth). Urinary Ca, serum Ca, Ca regulatory hormones (PTH, 1,25 dihydroxyvitamin D3 (1,25(OH)2D3)), bone parameters (µCT, ash), and renal/intestinal gene expression were analyzed. As expected, low dietary Ca intake negatively impacted bones and Lrp5A214V mice had higher bone mass and ash content. Although bones of Lrp5A214V mice have more matrix to mineralize, their bones were not more susceptible to low dietary Ca intake. In control mice, low dietary Ca intake exerted expected effects on serum Ca (decreased), PTH (increased), and 1,25(OH)2D3 (increased) as well as their downstream actions (ie, reducing urinary Ca, increasing markers of intestinal Ca absorption). In contrast, Lrp5A214V mice had elevated serum Ca with a normal PTH response but a blunted 1,25(OH)2D3 response to low dietary Ca that was reflected in the renal 1,25(OH)2D3 producing/degrading enzymes, Cyp27b1 and Cyp24a1. Despite elevated serum Ca in Lrp5A214V mice, urinary Ca was not elevated. Despite an abnormal serum 1,25(OH)2D3 response to low dietary Ca, intestinal markers of Ca absorption (Trpv6, S100g mRNA) were elevated in Lrp5A214V mice and responded to low Ca intake. Collectively, our data indicate that the Lrp5A214V mutation induces changes in Ca homeostasis that permit mice to retain more Ca and support their high bone mass phenotype.

Optimizing peak bone mass (PBM) is critical for strong bones and osteoporosis prevention. Both genetics and dietary factors like calcium (Ca) contribute to PBM. The goal of this research study was to determine how dietary Ca intake and genetics interact with each other to impact bone mass. Lowering dietary Ca in control mice causes hormonal changes that increase intestinal Ca absorption and reduce urinary Ca loss to protect bone; but this process fails when dietary Ca becomes too low. However, mice with genetically programmed high bone mass could maintain high bone mass even when challenged with Ca deficient diets. This protection is because the high bone mass mice maintain higher serum Ca, have altered production and utilization of Ca-regulating hormones, and have increased molecular indicators of intestinal Ca absorption and kidney Ca retention. Our findings are important because they demonstrate how a genetic program that increases bone formation can drive improved efficiency of Ca utilization to accommodate the increased need for Ca deposition into bone. We believe that our preclinical study provides important proof-of-principle support for the concept of personalized recommendations for bone health management.

Loss of maternal calcitriol reversibly alters early offspring growth and skeletal development in mice.

Ablation of Cyp27b1 eliminates calcitriol but does not disturb fetal mineral homeostasis or skeletal development. However, independent of fetal genotypes, maternal loss of Cyp27b1 altered fetal mineral and hormonal levels compared to offspring of WT dams. We hypothesized that these maternal influences would alter postnatal skeletal development. Cyp27b1 null and WT females were mated to bear only Cyp27b1+/- offspring. Forty-eight hours after birth, pups were cross-fostered to dams of the same or opposite genotype that bore them. Maternal and offspring samples were collected on days 21 (weaning) and 42. Offspring measurements included minerals and hormones, BMC by DXA, ash weight and mineral content, gene expression, 3-point bending tests, and microCT. Maternal lactational behavior was evaluated. Milk was analyzed for nutritional content. At day 21, offspring fostered by nulls, independent of birth dam, had ~20% lower weight, BMC, ash weight, and ash calcium than pups fostered by WT dams. Adjustment for body weight accounted for the lower BMC but not the lower ash weight and ash calcium. Hormones and serum/urine minerals did not differ across offspring groups. Offspring fostered by nulls had shorter femurs and lower cortical thickness, mean polar moment of inertia, cortical area, trabecular bone volume, and trabecular number. Dam lactational behaviors and milk nutritional content did not differ between groups. At day 42, body weight, ash weight, lengths, BMC, and tibial bone strength were no longer different between pups fostered by null vs WT dams. In summary, pups fostered by Cyp27b1 nulls, regardless of birth dam, have proportionately smaller skeletons at 21 d, impaired microstructure, but normal mineral homeostasis. The skeletal effects are largely recovered by day 42 (3 wk after weaning). In conclusion, maternal loss of calcitriol impairs early postnatal cortical bone growth and trabecular bone mass, but affected offspring catch up after weaning.

Calcitriol ameliorates motor deficits and prolongs survival of Chrne-deficient mouse, a model for congenital myasthenic syndrome, by inducing Rspo2.

Signal transduction at the neuromuscular junction (NMJ) is compromised in a diverse array of diseases including congenital myasthenic syndromes (CMS). Germline mutations in CHRNE encoding the acetylcholine receptor (AChR) ε subunit are the most common cause of CMS. An active form of vitamin D, calcitriol, binds to vitamin D receptor (VDR) and regulates gene expressions. We found that calcitriol enhanced MuSK phosphorylation, AChR clustering, and myotube twitching in co-cultured C2C12 myotubes and NSC34 motor neurons. RNA-seq analysis of co-cultured cells showed that calcitriol increased the expressions of Rspo2, Rapsn, and Dusp6. ChIP-seq of VDR revealed that VDR binds to a region approximately 15 â€‹kbp upstream to Rspo2. Biallelic deletion of the VDR-binding site of Rspo2 by CRISPR/Cas9 in C2C12 myoblasts/myotubes nullified the calcitriol-mediated induction of Rspo2 expression and MuSK phosphorylation. We generated Chrne knockout (Chrne KO) mouse by CRISPR/Cas9. Intraperitoneal administration of calcitriol markedly increased the number of AChR clusters, as well as the area, the intensity, and the number of synaptophysin-positive synaptic vesicles, in Chrne KO mice. In addition, calcitriol ameliorated motor deficits and prolonged survival of Chrne KO mice. In the skeletal muscle, calcitriol increased the gene expressions of Rspo2, Rapsn, and Dusp6. We propose that calcitriol is a potential therapeutic agent for CMS and other diseases with defective neuromuscular signal transmission.

Calcitriol suppresses gastric cancer progression and cisplatin resistance by inhibiting glycolysis and M2 macrophage polarization through inhibition of mTOR activation.

The tumor microenvironment (TME) plays a critical role in tumor progression, with macrophages and tumor cells interacting within the TME, influencing cancer development. Despite the known anticancer properties of calcitriol, its role in the TME remains uncertain. This study aimed to explore the effects of calcitriol on macrophages and cancer cells in the TME and its impact on gastric cancer cell proliferation and cisplatin resistance. In vitro TME models were established using conditioned medium from gastric cancer cells (CCM) and macrophages (MCM) treated with or without calcitriol. The results revealed that calcitriol treatment suppressed the expression of glycolysis-related genes and proteins (GLUT1, HKII, LDHA) in MCM-induced gastric cancer cells, leading to increased cancer cell apoptosis and reduced viability, along with decreased Cyclin D1 gene expression. Moreover, calcitriol treatment inhibited mTOR activation in MCM-induced gastric cancer cells. Additionally, calcitriol hindered CCM-induced M2 macrophage polarization by reducing CD206 expression and increasing TNFα gene expression in THP1-derived macrophages, attenuating cisplatin resistance. These findings suggest that calcitriol may impede gastric cancer progression by targeting glycolysis and M2 macrophage polarization through the regulation of mTOR activation in the TME.

Immunomodulatory Nanoparticles for Modulating Arthritis Flares.

Disease-modifying drugs have improved the treatment for autoimmune joint disorders, such as rheumatoid arthritis, but inflammatory flares are a common experience. This work reports the development and application of flare-modulating poly(lactic-co-glycolic acid)-poly(ethylene glycol)-maleimide (PLGA-PEG-MAL)-based nanoparticles conjugated with joint-relevant peptide antigens, aggrecan70-84 and type 2 bovine collagen256-270. Peptide-conjugated PLGA-PEG-MAL nanoparticles encapsulated calcitriol, which acted as an immunoregulatory agent, and were termed calcitriol-loaded nanoparticles (CLNP). CLNP had a ∼200 nm hydrodynamic diameter with a low polydispersity index. In vitro, CLNP induced phenotypic changes in bone marrow derived dendritic cells (DC), reducing the expression of costimulatory and major histocompatibility complex class II molecules, and proinflammatory cytokines. Bulk RNA sequencing of DC showed that CLNP enhanced expression of Ctla4, a gene associated with downregulation of immune responses. In vivo, CLNP accumulated in the proximal lymph nodes after intramuscular injection. Administration of CLNP was not associated with changes in peripheral blood cell numbers or cytokine levels. In the collagen-induced arthritis and SKG mouse models of autoimmune joint disorders, CLNP reduced clinical scores, prevented bone erosion, and preserved cartilage proteoglycan, as assessed by high-resolution microcomputed tomography and histomorphometry analysis. The disease protective effects were associated with increased CTLA-4 expression in joint-localized DC and CD4+ T cells but without generalized suppression of T cell-dependent immune response. The results support the potential of CLNP as modulators of disease flares in autoimmune arthropathies.

Different impact of vitamin D on mitochondrial activity and morphology in normal and malignant keratinocytes, the role of genomic pathway.

Deregulation of mitochondria activity is one of the hallmarks of cancerogenesis and an important target for cancer therapy. Therefore, we compared the impact of an active form of vitamin D3 (1,25(OH)2D3) on mitochondrial morphology and bioenergetics in human squamous cell carcinoma (A431) and immortalized HaCaT keratinocytes. It was shown that mitochondria of cancerous A431 cells differ from that observed in HaCaT keratinocytes in terms of network, morphology, bioenergetics, glycolysis, and mitochondrial DNA copy number, while treatment of A431 with 1,25(OH)2D3 partially eliminates these differences. Furthermore, mitochondrial membrane potential, basal respiration, and mitochondrial reactive oxygen species production were decreased in A431 cells treated with 1,25(OH)2D3. Additionally, the expression and protein level of mitophagy marker PINK1 was significantly increased in A431 1,25(OH)2D3 treated cells, but not observed in treated HaCaT cells. Knockout of VDR (vitamin D receptor) or RXRA (binding partner retinoid X receptor) partially altered mitochondrial morphology and function as well as mitochondrial response to 1,25(OH)2D3. Transcriptomic analysis on A431 cells treated with 1,25(OH)2D3 revealed modulation of expression of several mitochondrial-related genes involved in mitochondrial depolarization, mitochondrial protein translation (i.e. LYRM9, MARS2), and fusion-fission (OPA1, FIS1, MFN1 and 2), however, none of the genes coded by mitochondrial DNA was affected. Interestingly, in silico analyses of nuclear-encoded mitochondrial genes revealed that they are rather activated by the secondary genomic response to 1,25(OH)2D3. Taken together, 1,25(OH)2D3 remodels mitochondrial architecture and bioenergetics through VDR-dependent and only partially RXRA-dependent activation of the genomic pathway, thus outlining a new perspective for anticancer properties of vitamin D3 in relation to mitochondria in squamous cell carcinoma.

Transcriptional landscape of human trophoblast cells treated with calcitriol and TGF-ß1.

Calcitriol and transforming growth factor beta 1 (TGF-ß1) are unrelated molecules that regulate biological processes according to the genetic target, cell type, and context. Several studies have shown independent effects of calcitriol and TGF-ßs on the placenta, but there is no information regarding the impact of their combination on these cells. Therefore, this study analyzed the effects of calcitriol, TGF-ß1, and their combination in primary cultures of human trophoblast cells using a whole genome expression microarray. Data analysis revealed a set of differentially expressed genes induced by each treatment. Enrichment pathway analysis identified modulatory effects of calcitriol on genes related to metabolic processes such as vitamin D, steroid, and fat-soluble vitamins as well as antimicrobial and immune responses. In relation to TGF-ß1, the analysis showed a few differentially expressed genes that were mainly associated with the neutrophil immune response. Lastly, the analysis revealed that the combination of calcitriol and TGF-ß1 up-regulated genes involving both immunologic processes and the biosynthesis of unsaturated fatty acids, eicosanoids, and lipoxins, among others. In contrast, pathways down-regulated by the combination were mostly associated with the catabolic process of acylglycerols and peptides, PPAR signaling pathway, cellular response to low-density lipoprotein stimulus, renin angiotensin system and digestion, mobilization and transport of lipids. Consistent with these results, the combined treatment on human trophoblast cells induced the accumulation of intracellular neutral lipid droplets and stimulated both gene and protein expression of 15-hydroxyprostaglandin dehydrogenase. In conclusion, the results revealed that differentially expressed genes induced by the combination modified the transcriptional landscape compared to each treatment alone, mainly altering the storage, activity and metabolism of lipids, which might have an impact on placental development.

Dissection of an impact of VDR and RXRA on the genomic activity of 1,25(OH)2D3 in A431 squamous cell carcinoma.

BACKGROUND: Human skin is the natural source, place of metabolism, and target for vitamin D3. The classical active form of vitamin D3, 1,25(OH)2D3, expresses pluripotent properties and is intensively studied in cancer prevention and therapy. To define the specific role of vitamin D3 receptor (VDR) and its co-receptor retinoid X receptor alpha (RXRA) in genomic regulation, VDR or RXRA genes were silenced in the squamous cell carcinoma cell line A431 and treated with 1,25(OH)2D3 at long incubation time points 24 h/72 h. Extending the incubation time of A431 WT (wild-type) cells with 1,25(OH)2D3 resulted in a two-fold increase in DEGs (differentially expressed genes) and a change in the amount of downregulated from 37% to 53%. VDR knockout led to a complete loss of 1,25(OH)2D3-induced genome-wide gene regulation at 24 h time point, but after 72 h, 20 DEGs were found, of which 75% were downregulated, and most of them belonged to the gene ontology group "immune response". This may indicate the existence of an alternative, secondary response to 1,25(OH)2D3. In contrast, treatment of A431 ΔRXRA cells with 1,25(OH)2D3 for 24 h only partially affected DEGs, suggesting RXRA-independent regulation. Interestingly, overexpression of classic 1,25(OH)2D3 targets, like CYP24A1 (family 24 of subfamily A of cytochrome P450 member 1) or CAMP (cathelicidin antimicrobial peptide) was found to be RXRA-independent. Also, immunofluorescence staining of A431 WT cells revealed partial VDR/RXRA colocalization after 24 h and 72 h 1,25(OH)2D3 treatment. Comparison of transcriptome changes induced by 1,25(OH)2D3 in normal keratinocytes vs. cancer cells showed high cell type specific expression pattern with only a few genes commonly regulated by 1,25(OH)2D3. Activation of the genomic pathway at least partially reversed the expression of cancer-related genes, forming a basis for anti-cancer activates of 1,25(OH)2D3. In summary, VDR or RXRA independent genomic activities of 1,25(OH)2D3 suggest the involvement of alternative factors, opening new challenges in this field.

1,25-Dihydroxyvitamin D3 Provides Benefits in Vitiligo Based on Modulation of CD8+ T Cell Glycolysis and Function.

Vitiligo is a common autoimmune skin disease caused by autoreactive CD8+ T cells. The diverse effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on immune cell metabolism and proliferation have made it an interesting candidate as a supporting therapeutic option in various autoimmune diseases. This study aimed to elucidate the immunomodulatory effects of 1,25(OH)2D3 in vitiligo. Cross-sectional relationships between serum 1,25(OH)2D3 levels and disease characteristics were investigated in 327 patients with vitiligo. The immunomodulatory and therapeutic effects of 1,25(OH)2D3 were then investigated in vivo and in vitro, respectively. We found that 1,25(OH)2D3 deficiency was associated with hyperactivity of CD8+ T cells in the vitiligo cohort. In addition, 1,25(OH)2D3 suppressed glycolysis by activating the AMP-activated protein kinase (AMPK) signaling pathway, thereby inhibiting the proliferation, cytotoxicity and aberrant activation of CD8+ T cells. Finally, the in vivo administration of 1,25(OH)2D3 to melanocyte-associated vitiligo (MAV) mice reduced the infiltration and function of CD8+ T cells and promoted repigmentation. In conclusion, 1,25(OH)2D3 may serve as an essential biomarker of the progression and severity of vitiligo. The modulation of autoreactive CD8+ T cell function and glycolysis by 1,25(OH)2D3 may be a novel approach for treating vitiligo.

Neuroprotective effect of 1,25­dihydroxyvitamin D3 against hyperoxia­induced brain injury in premature rats.

Studies have shown that vitamin D plays a crucial role in brain development, brain metabolism and neuroprotection. There is little evidence for the neuroprotective effect of 1, 25­dihydroxyvitamin D3 (1,25­(OH)2D3) on various brain injury models. The aim of this study was to investigate the neuroprotection effect of 1,25­(OH)2D3 against hyperoxia­induced brain injury in premature rats. Sprague­Dawley rats were exposed to 95% oxygen or room air for 24 h and treated with 1,25­(OH)2D3 or normal saline for 14 consecutive days. The histopathological changes of optic chiasma tissue were observed by hematoxylin­eosin staining. Immunohistochemistry, qRT­PCR, and western blot were performed to detect the expression of integrin­ß1 and yes­associated protein (YAP) in the organization of the optic chiasm. Histopathological sections of optic chiasma showed visible optic nerve swelling, expanded nerve fiber space, uneven staining, obvious oligodendrocyte proliferation and disordered cell arrangement accompanied by inflammatory cell infiltration and exudation after 7 days and 14 days of hyperoxia exposure. The hyperoxia group treated with 1,25­(OH)2D3 were showed improvement of brain injury with reduced inflammatory exudation, uniform nerve fiber staining and less obvious oligodendrocyte proliferation. Immunohistochemical staining, qRT­PCR and western blot indicated that 1,25­(OH)2D3 treatment upregulated the expression of integrin­ß1 and YAP in the hyperoxia group on day 7. However, the expression of YAP was significantly increased compared with control group and treatment with 1,25­(OH)2D3 reduced the expression of YAP in the hyperoxic group on day 14. 1,25­(OH)2D3 may regulate the expression of integrin­ß1 and YAP to alleviate hyperoxia­induced brain injury in premature rats.

Inhibition of LAMP3 mediates the protective effect of vitamin D against hypoxia/reoxygenation in trophoblast cells.

Inadequate invasion and excessive apoptosis of trophoblast cells are associated with the development of preeclampsia. Vitamin D deficiency in pregnant women may lead to an increased risk of preeclampsia. However, the underlying mechanisms by which vitamin D is effective in preventing preeclampsia are not fully understood. The objectives of this study were to investigate the role of lysosome-associated membrane glycoprotein 3 (LAMP3) in the pathogenesis of preeclampsia and to evaluate whether vitamin D supplementation would protect against the development of preeclampsia by regulating LAMP3 expression. Firstly, the mRNA and protein levels of LAMP3 were significantly upregulated in the placentas of preeclampsia patients compared to normal placentas, especially in trophoblast cells (a key component of the human placenta). In the hypoxia/reoxygenation (H/R)-exposed HTR-8/Svneo trophoblast cells, LAMP3 expression was also upregulated. H/R exposure repressed cell viability and invasion and increased apoptosis of trophoblast cells. siRNA-mediated knockdown of LAMP3 increased cell viability and invasion and suppressed apoptosis of H/R-exposed trophoblast cells. We further found that 1,25(OH)2D3 (the hormonally active form of vitamin D) treatment reduced LAMP3 expression in H/R exposed trophoblast cells. In addition, 1,25(OH)2D3 treatment promoted cell viability and invasion and inhibited apoptosis of H/R-exposed trophoblast cells. Notably, overexpression of LAMP3 abrogated the protective effect of 1,25(OH)2D3 on H/R-exposed trophoblast cells. Collectively, we demonstrated trophoblast cytoprotection by vitamin D, a process mediated via LAMP3.