Comparative Morpho-Anatomical and HPTLC Profiling of Tinospora Species and Dietary Supplements.

Overlapping geographical occurrence, history of traditional use, confusion in species identification, and morphological resemblances among various species are some considerations that necessitate the importance of qualitative analysis for efficient quality control and safer botanical products. This paper provides detailed morpho-anatomies of the leaves and stems of Tinospora cordifolia, Tinospora crispa, and Tinospora sinensis, and stems of Tinospora baenzigeri. Microscopy studies of the selected Tinospora species revealed key diagnostic features that can help distinguish the closely related species of Tinospora as well as to detect any adulteration or substitution in the raw materials. HPTLC profiles of the authenticated plant materials, as well as commercial products claiming to contain Tinospora, were compared to distinguish T. crispa from other closely related species and to establish an efficient method to assess the identity and quality of the products using qualified chemical markers. HPTLC chromatograms of both plant samples and dietary supplements were compared with six reference marker compounds. The analysis revealed that borapetoside B and C were useful to identify T. crispa while tinosineside A was found to be characteristic to authenticate the T. sinensis products.

Preoperative Vitamin D Repletion in Total Knee Arthroplasty: A Cost-Effectiveness Model.

BACKGROUND: Recent studies have identified vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] < 20 ng/L) as a potentially modifiable risk factor for prosthetic joint infection (PJI) in arthroplasty. The purpose of this study is to determine whether implementation of preoperative 25(OH)D repletion is cost-effective for reducing PJI following total knee arthroplasty (TKA). METHODS: A cost estimation predictive model was generated to determine the utility of both selective and nonselective 25(OH)D repletion in primary TKA to prevent PJI. Input data on the incidence of 25(OH)D deficiency, relative complication rates, and costs of serum 25(OH)D repletion and 2-stage revision for PJI were derived from previously published literature identified using systematic review and publicly available data from Medicare reimbursement schedules. Mean, lower, and upper bounds of 1-year cost savings were computed for nonselective and selective repletion relative to no repletion. RESULTS: Selective preoperative 25(OH)D screening and repletion were projected to result in $1,504,857 (range, $215,084-$4,256,388) in cost savings per 10,000 cases. Nonselective 25(OH)D repletion was projected to result in $1,906,077 (range, $616,304-$4,657,608) in cost savings per 10,000 cases. With univariate adjustment, nonselective repletion is projected to be cost-effective in scenarios where revision for PJI costs ≥$10,636, incidence of deficiency is ≥1.1%, and when repletion has a relative risk reduction ≥4.2%. CONCLUSION: This predictive model supports the potential role of 25(OH)D repletion as a cost-effective mechanism of reducing PJI risk in TKA. Given the low cost of 25(OH)D repletion relative to serum laboratory testing, nonselective repletion appears to be more cost-effective than selective repletion. Further prospective investigation to assess this modifiable risk factor is warranted.

Concerted effects of heterogeneous nuclear ribonucleoprotein C1/C2 to control vitamin D-directed gene transcription and RNA splicing in human bone cells.

Traditionally recognized as an RNA splicing regulator, heterogeneous nuclear ribonucleoprotein C1/C2 (hnRNPC1/C2) can also bind to double-stranded DNA and function in trans as a vitamin D response element (VDRE)-binding protein. As such, hnRNPC1/C2 may couple transcription induced by the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D) with subsequent RNA splicing. In MG63 osteoblastic cells, increased expression of the 1,25(OH)2D target gene CYP24A1 involved immunoprecipitation of hnRNPC1/C2 with CYP24A1 chromatin and RNA. Knockdown of hnRNPC1/C2 suppressed expression of CYP24A1, but also increased expression of an exon 10-skipped CYP24A1 splice variant; in a minigene model the latter was attenuated by a functional VDRE in the CYP24A1 promoter. In genome-wide analyses, knockdown of hnRNPC1/C2 resulted in 3500 differentially expressed genes and 2232 differentially spliced genes, with significant commonality between groups. 1,25(OH)2D induced 324 differentially expressed genes, with 187 also observed following hnRNPC1/C2 knockdown, and a further 168 unique to hnRNPC1/C2 knockdown. However, 1,25(OH)2D induced only 10 differentially spliced genes, with no overlap with differentially expressed genes. These data indicate that hnRNPC1/C2 binds to both DNA and RNA and influences both gene expression and RNA splicing, but these actions do not appear to be linked through 1,25(OH)2D-mediated induction of transcription.

Redesign of chronic illness care in children and adolescents: evidence for the chronic care model.

PURPOSE OF REVIEW: This article provides an overview of the chronic care model (CCM), examines the evidence for its utility in pediatric and adolescent chronic illness, and discusses practical steps for improving chronic illness care in the pediatric medical home. RECENT FINDINGS: Few studies have used the CCM as an improvement framework in pediatrics. However, in recent years, several quality improvement efforts based on the CCM have demonstrated improvement in important process measures or clinical outcomes in pediatric or adolescent obesity, inflammatory bowel disease, attention-deficit/hyperactivity disorder, depression, and asthma. SUMMARY: The CCM is an improvement framework that has demonstrated success in improving the care of children and adolescents with chronic disease. More research is needed to identify priority conditions for improvement efforts, to better understand the mediators of health outcomes in pediatric chronic disease, and to rigorously demonstrate the effectiveness of new models of chronic illness care. The evidence to date suggests that the CCM may be useful in guiding the redesign of care delivery systems to improve the health outcomes of young people with chronic disease.

Cloning of a functional 25-hydroxyvitamin D-1α-hydroxylase in zebrafish (Danio rerio).

Activation of precursor 25-hydroxyvitamin D3 (25D) to hormonal 1,25-dihydroxyvitamin D3 (1,25D) is a pivotal step in vitamin D physiology, catalysed by the enzyme 25-hydroxyvitamin D-1α-hydroxylase (1α-hydroxylase). To establish new models for assessing the physiological importance of the 1α-hydroxylase-25D-axis, we used Danio rerio (zebrafish) to characterize expression and biological activity of the gene for 1α-hydroxylase (cyp27b1). Treatment of day 5 zebrafish larvae with inactive 25D (5-150 nM) or active 1,25D (0.1-10 nM) induced dose responsive expression (15-95-fold) of the vitamin D-target gene cyp24a1 relative to larvae treated with vehicle, suggesting the presence of Cyp27b1 activity. A full-length zebrafish cyp27b1 cDNA was then generated using RACE and RT-PCR methods. Sequencing of the resulting clone revealed an open reading frame encoding a protein of 505 amino acids with 54% identity to human CYP27B1. Transfection of a cyp27b1 expression vector into HKC-8, a human kidney proximal tubular epithelial cell line, enhanced intracrine metabolism of 25D to 1,25D resulting in greater than twofold induction of CYP24A1 mRNA expression and a 25-fold increase in 1,25D production compared to empty vector. These data indicate that we have cloned a functional zebrafish CYP27B1, representing a phylogenetically distant branch from mammals of this key enzyme in vitamin D metabolism. Further analysis of cyp27b1 expression and activity in zebrafish may provide new perspectives on the biological importance of 25D metabolism.

Vitamin D and microRNAs in bone.

MicroRNAs (miRNAs) are short noncoding RNAs that orchestrate complex posttranscriptional regulatory networks essential to the regulation of gene expression. Through complementarity with messenger RNA (mRNA) sequences, miRNAs act primarily to silence gene expression through either degradation or inhibited translation of target transcripts. In this way, miRNAs can act to fine-tune the transcriptional regulation of gene expression, but they may also play distinct roles in the proliferation, differentiation, and function of specific cell types. miRNA regulatory networks may be particularly important for signaling molecules such as vitamin D that exert pleiotropic effects on tissues throughout the body. The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D) functions as a steroid hormone that, when bound to its nuclear vitamin D receptor, is able to regulate target gene expression. However, recent studies have also implicated 1,25(OH)2D in epigenetic regulation of genes most notably as a modulator of miRNA function. The current review details our understanding of vitamin D and miRNAs with specific emphasis on the implications of this interaction for biological responses to vitamin D in one of its classical target tissues, i.e., bone.

T-cell cytokines differentially control human monocyte antimicrobial responses by regulating vitamin D metabolism.

We investigated the mechanisms by which T-cell cytokines are able to influence the Toll-like receptor (TLR)-induced, vitamin D-dependent antimicrobial pathway in human monocytes. T-cell cytokines differentially influenced TLR2/1-induced expression of the antimicrobial peptides cathelicidin and DEFB4, being up-regulated by IFN-γ, down-regulated by IL-4, and unaffected by IL-17. The Th1 cytokine IFN-γ up-regulated TLR2/1 induction of 25-hydroxyvitamin D-1α-hydroxylase (i.e., CYP27B1), leading to enhanced bioconversion of 25-hydroxyvitamin D(3) (25D(3)) to its active metabolite 1,25D(3). In contrast, the Th2 cytokine IL-4, by itself and in combination with the TLR2/1 ligand, induced catabolism of 25D(3) to the inactive metabolite 24,25D(3), and was dependent on expression of vitamin D-24-hydroxylase (i.e., CYP24A1). Therefore, the ability of T-cell cytokines to differentially control monocyte vitamin D metabolism represents a mechanism by which cell-mediated immune responses can regulate innate immune mechanisms to defend against microbial pathogens.

High-Throughput CAMP Assay (HiTCA): A Novel Tool for Evaluating the Vitamin D-Dependent Antimicrobial Response.

Vitamin D is known to modulate human immune responses, and vitamin D deficiency is associated with increased susceptibility to infection. However, what constitutes sufficient levels or whether vitamin D is useful as an adjuvant therapeutic is debated, much in part because of inadequate elucidation of mechanisms underlying vitamin D's immune modulatory function. Cathelicidin antimicrobial peptide (CAMP) has potent broad-spectrum activity, and the CAMP gene is regulated in human innate immune cells by active 1,25(OH)2D3, a product of hydroxylation of inactive 25(OH)D3 by CYP27B1-hydroxylase. We developed a CRISPR/Cas9-edited human monocyte-macrophage cell line containing the mCherry fluorescent reporter gene at the 3' end of the endogenous CAMP gene. The High Throughput CAMP Assay (HiTCA) developed here is a novel tool for evaluating CAMP expression in a stable cell line that is scalable for a high-throughput workflow. Application of HiTCA to serum samples from a small number of human donors (n = 10) showed individual differences in CAMP induction that were not fully accounted for by the serum vitamin D metabolite status of the host. As such, HiTCA may be a useful tool that can advance our understanding of the human vitamin D-dependent antimicrobial response, which is being increasingly appreciated for its complexity.

REsCue trial: Randomized controlled clinical trial with extended-release calcifediol in symptomatic COVID-19 outpatients.

OBJECTIVES: This double-blind randomized controlled trial investigated raising serum 25-hydroxyvitamin D (25D) with extended-release calcifediol (ERC) on time to symptom resolution in patients with mild to moderate COVID-19. METHODS: COVID-19 outpatients received oral ERC (300 mcg on days 1-3 and 60 mcg on days 4-27) or placebo (NCT04551911). Symptoms were self-reported daily. Primary end points were raising 25D to ≥50 ng/mL and decreasing resolution time for five aggregated symptoms (three respiratory). RESULTS: In all, 171 patients were randomized, 160 treated and 134 (65 ERC, 69 placebo) retained. The average age was 43 y (range 18-71), 59% were women. The mean baseline 25D was 37 ± 1 (SE) ng/mL. In the full analysis set (FAS), 81% of patients in the ERC group achieved 25D levels of ≥50 ng/mL versus 15% in the placebo group (P < 0.0001). In the per-protocol (PP) population, mean 25D increased with ERC to 82 ± 4 (SE) ng/mL (P < 0.0001) by day 7; the placebo group trended lower. Symptom resolution time was unchanged in the FAS by ERC (hazard ratio [HR], 0.983; 95% confidence interval [CI], 0.695-1.390; P = 0.922). In the PP population, respiratory symptoms resolved 4 d faster when 25D was elevated above baseline level at both days 7 and 14 (median 6.5 versus 10.5 d; HR, 1.372; 95% CI, 0.945-1.991; P = 0.0962; Wilcoxon P = 0.0386). Symptoms resolved in both treatment groups to a similar extent by study end. Safety concerns including hypercalcemia were absent with ERC treatment. CONCLUSION: ERC safely raised serum 25D to ≥50 ng/mL in outpatients with COVID-19, possibly accelerating resolution of respiratory symptoms and mitigating the risk for pneumonia. These findings warrant further study.

Gene targeting by the vitamin D response element binding protein reveals a role for vitamin D in osteoblast mTOR signaling.

Transcriptional regulation by hormonal 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] involves occupancy of vitamin D response elements (VDREs) by the VDRE binding protein (VDRE-BP) or 1,25(OH)(2)D(3)-bound vitamin D receptor (VDR). This relationship is disrupted by elevated VDRE-BP, causing a form of hereditary vitamin D-resistant rickets (HVDRR). DNA array analysis showed that of 114 genes regulated by 1,25(OH)(2)D(3) in control cells, almost all (113) were rendered insensitive to the hormone in VDRE-BP-overexpressing HVDRR cells. Among these was the gene for DNA-damage-inducible transcript 4 (DDIT4), an inhibitor of mammalian target of rapamycin (mTOR) signaling. Chromatin immunoprecipitation PCR using 1,25(OH)(2)D(3)-treated osteoblasts confirmed that VDR and VDRE-BP compete for binding to the DDIT4 gene promoter. Expression of DDIT4 mRNA in these cells was induced (1.6-6 fold) by 1,25(OH)(2)D(3) (10-100 nM), and Western blot and flow cytometry analysis showed that this response involved suppression of phosphorylated S6K1(T389) (a downstream target of mTOR) similar to rapamycin treatment. siRNA knockdown of DDIT4 completely abrogated antiproliferative responses to 1,25(OH)(2)D(3), whereas overexpression of VDRE-BP exerted a dominant-negative effect on transcription of 1,25(OH)(2)D(3)-target genes. DDIT4, an inhibitor of mTOR signaling, is a direct target for 1,25(OH)(2)D(3) and VDRE-BP, and functions to suppress cell proliferation in response to vitamin D.

Alternative splicing diversifies the skeletal muscle transcriptome during prolonged spaceflight.

BACKGROUND: As the interest in manned spaceflight increases, so does the requirement to understand the transcriptomic mechanisms that underlay the detrimental physiological adaptations of skeletal muscle to microgravity. While microgravity-induced differential gene expression (DGE) has been extensively investigated, the contribution of differential alternative splicing (DAS) to the plasticity and functional status of the skeletal muscle transcriptome has not been studied in an animal model. Therefore, by evaluating both DGE and DAS across spaceflight, we set out to provide the first comprehensive characterization of the transcriptomic landscape of skeletal muscle during exposure to microgravity. METHODS: RNA-sequencing, immunohistochemistry, and morphological analyses were conducted utilizing total RNA and tissue sections isolated from the gastrocnemius and quadriceps muscles of 30-week-old female BALB/c mice exposed to microgravity or ground control conditions for 9 weeks. RESULTS: In response to microgravity, the skeletal muscle transcriptome was remodeled via both DGE and DAS. Importantly, while DGE showed variable gene network enrichment, DAS was enriched in structural and functional gene networks of skeletal muscle, resulting in the expression of alternatively spliced transcript isoforms that have been associated with the physiological changes to skeletal muscle in microgravity, including muscle atrophy and altered fiber type function. Finally, RNA-binding proteins, which are required for regulation of pre-mRNA splicing, were themselves differentially spliced but not differentially expressed, an upstream event that is speculated to account for the downstream splicing changes identified in target skeletal muscle genes. CONCLUSIONS: Our work serves as the first investigation of coordinate changes in DGE and DAS in large limb muscles across spaceflight. It opens up a new opportunity to understand (i) the molecular mechanisms by which splice variants of skeletal muscle genes regulate the physiological adaptations of skeletal muscle to microgravity and (ii) how small molecule splicing regulator therapies might thwart muscle atrophy and alterations to fiber type function during prolonged spaceflight.

Vitamin D in HIV-Infected Patients.

Observational studies have noted very high rates of low 25(OH)D (vitamin D) levels in both the general and HIV-infected populations. In HIV-infected patients, low 25(OH)D levels are likely a combination of both traditional risk factors and HIV-specific and antiretroviral therapy-specific contributors. Because of this unique risk profile, HIV-infected persons may be at greater risk for low 25(OH)D levels and frank deficiency and/or may respond to standard repletion regimens differently than HIV-uninfected patients. Currently, the optimal repletion and maintenance dosing regimens for HIV-infected patients remain unknown, as do potential benefits of supplementation that may be unique to the HIV-infected population. This paper reviews data published on HIV infection and vitamin D health in adults over the last year.

Vitamin d-directed rheostatic regulation of monocyte antibacterial responses.

The active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D) enhances innate immunity by inducing the cathelicidin antimicrobial peptide (hCAP). In monocytes/macrophages, this occurs primarily in response to activation of TLR, that induce expression of the vitamin D receptor and localized synthesis of 1,25(OH)(2)D from precursor 25-hydroxyvitamin D(3) (25OHD). To clarify the relationship between vitamin D and innate immunity, we assessed changes in hCAP expression in vivo and ex vivo in human subjects attending a bone clinic (n = 50). Of these, 38% were vitamin D-insufficient (<75 nM 25OHD) and received supplementation with vitamin D (50,000 IU vitamin D(2) twice weekly for 5 wk). Baseline 25OHD status or vitamin D supplementation had no effect on circulating levels of hCAP. Therefore, ex vivo changes in hCAP for each subject were assessed using peripheral blood monocytes cultured with 10% autologous serum (n = 28). Under these vitamin D "insufficient" conditions the TLR2/1 ligand 19 kDa lipopeptide or the TLR4 ligand LPS, monocytes showed increased expression of the vitamin D-activating enzyme CYP27b1 (5- and 5.5-fold, respectively, both p < 0.01) but decreased expression of hCAP mRNA (10-fold and 30-fold, both p < 0.001). Following treatment with 19 kDa, expression of hCAP: 1) correlated with 25OHD levels in serum culture supplements (R = 0.649, p < 0.001); 2) was significantly enhanced by exogenous 25OHD (5 nM); and 3) was significantly enhanced with serum from vivo vitamin D-supplemented patients. These data suggest that a key role of vitamin D in innate immunity is to maintain localized production of antibacterial hCAP following TLR activation of monocytes.

Pilot Trial of Vitamin D3 and Calcifediol in Healthy Vitamin D Deficient Adults: Does It Change the Fecal Microbiome?

CONTEXT: Experimental studies suggest that vitamin D receptor signaling may benefit the gut microbiome. In humans, whether vitamin D supplementation directly alters the gut microbiome is not well studied. OBJECTIVE: To determine whether correcting vitamin D deficiency with cholecalciferol (vitamin D3, D3) or calcifediol (25-hydroxyvitamin D3, 25(OH)D3) changes gut microbiome composition. METHODS: 18 adults with vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] <20 ng/mL) received 60 µg/day of D3 or 20 µg/day of 25(OH)D3 for 8 weeks. Changes in serum 25(OH)D, 1,25-diydroxyvitamin D (1,25(OH)2D), and 24,25-dihydroxyvitamin D (24,25(OH)2D) were assessed. We characterized composition of the fecal microbiota using 16S rRNA gene sequencing, and examined changes in α-diversity (Chao 1, Faith's Phylogenetic Diversity, Shannon Index), ß-diversity (DEICODE), and genus-level abundances (DESeq2). RESULTS: Vitamin D3 and 25(OH)D3 groups were similar. After 8 weeks of vitamin D3, mean 25(OH)D and 24,25(OH)2D increased significantly, but 1,25(OH)2D did not (25(OH)D: 17.8-30.1 ng/mL, P = .002; 24,25(OH)2D: 1.1 to 2.7 ng/mL, P =0.003; 1,25(OH)2D: 49.5-53.0 pg/mL, P = .9). After 8 weeks of 25(OH)D3, mean 25(OH)D, 24,25(OH)2D, and 1,25(OH)2D increased significantly (25(OH)D: 16.7-50.6 ng/mL, P < .0001; 24,25(OH)2D: 1.3-6.2 ng/mL, P = .0001; 1,25(OH)2D: 56.5-74.2 pg/mL, P = .05). Fecal microbial α-diversity and ß-diversity did not change with D3 or 25D3 supplementation. Mean relative abundance of Firmicutes increased and mean relative abundance of Bacterioidetes decreased from baseline to 4 weeks, but returned to baseline by study completion. DESeq2 analysis did not confirm any statistically significant taxonomic changes. CONCLUSION: In a small sample of healthy adults with vitamin D deficiency, restoration of vitamin D sufficiency with vitamin D3 or 25(OH)D3 did not lead to lasting changes in the fecal microbiota.

IL-15 links TLR2/1-induced macrophage differentiation to the vitamin D-dependent antimicrobial pathway.

An essential function of the innate immune system is to directly trigger antimicrobial mechanisms to defend against invading pathogens. In humans, one such pathway involves activation by TLR2/1L leading to the vitamin D-dependent induction of antimicrobial peptides. In this study, we found that TLR2/1-induced IL-15 was required for induction of CYP27b1, the VDR and the downstream antimicrobial peptide cathelicidin. Although both IL-15 and IL-4 triggered macrophage differentiation, only IL-15 was sufficient by itself to induce CYP27b1 and subsequent bioconversion of 25-hydroxyvitamin D3 (25D3) into bioactive 1,25D3, leading to VDR activation and induction of cathelicidin. Finally, IL-15-differentiated macrophages could be triggered by 25D3 to induce an antimicrobial activity against intracellular Mycobacterium tuberculosis. Therefore, IL-15 links TLR2/1-induced macrophage differentiation to the vitamin D-dependent antimicrobial pathway.

Vitamin D metabolites and the gut microbiome in older men.

The vitamin D receptor is highly expressed in the gastrointestinal tract where it transacts gene expression. With current limited understanding of the interactions between the gut microbiome and vitamin D, we conduct a cross-sectional analysis of 567 older men quantifying serum vitamin D metabolites using LC-MSMS and defining stool sub-Operational Taxonomic Units from16S ribosomal RNA gene sequencing data. Faith's Phylogenetic Diversity and non-redundant covariate analyses reveal that the serum 1,25(OH)2D level explains 5% of variance in α-diversity. In ß-diversity analyses using unweighted UniFrac, 1,25(OH)2D is the strongest factor assessed, explaining 2% of variance. Random forest analyses identify 12 taxa, 11 in the phylum Firmicutes, eight of which are positively associated with either 1,25(OH)2D and/or the hormone-to-prohormone [1,25(OH)2D/25(OH)D] "activation ratio." Men with higher levels of 1,25(OH)2D and higher activation ratios, but not 25(OH)D itself, are more likely to possess butyrate producing bacteria that are associated with better gut microbial health.

CCN1/Cyr61 Is Required in Osteoblasts for Responsiveness to the Anabolic Activity of PTH.

CCN1/Cyr61 is a dynamically expressed matricellular protein that serves regulatory functions in multiple tissues. Previous studies from our laboratory demonstrated that CCN1 regulates bone maintenance. Using an osteoblast and osteocyte conditional knockout mouse model (Ccn1OCN ), we found a significant decrease in trabecular and cortical bone mass in vivo, in part through suppression of Wnt signaling since the expression of the Wnt antagonist sclerostin (SOST) is increased in osteoblasts lacking CCN1. It has been established that parathyroid hormone (PTH) signaling also suppresses SOST expression in bone. We therefore investigated the interaction between CCN1 and PTH-mediated responses in this study. We find that loss of Ccn1 in osteoblasts leads to impaired responsiveness to anabolic intermittent PTH treatment in Ccn1OCN mice in vivo and in osteoblasts from these mice in vitro. Analysis of Ccn1OCN mice demonstrated a significant decrease in parathyroid hormone receptor-1 (PTH1R) expression in osteoblasts in vivo and in vitro. We investigated the regulatory role of a non-canonical integrin-binding domain of CCN1 because several studies indicate that specific integrins are critical to mechanotransduction, a PTH-dependent response, in bone. These data suggest that CCN1 regulates the expression of PTH1R through interaction with the αvß3 and/or αvß5 integrin complexes. Osteoblasts that express a mutant form of CCN1 that cannot interact with αvß3/ß5 integrin demonstrate a significant decrease in mRNA and protein expression of both PTH1R and αv integrin. Overall, these data suggest that the αvß3/ß5-binding domain of CCN1 is required to endow PTH signaling with anabolic activity in bone cells. © 2020 American Society for Bone and Mineral Research (ASBMR).

Control of estradiol-directed gene transactivation by an intracellular estrogen-binding protein and an estrogen response element-binding protein.

New World primates exhibit a form of resistance to estrogens that is associated with overexpression of an estrogen response element (ERE)-binding protein (ERE-BP) and an intracellular estradiol (E(2))-binding protein (IEBP). Both proteins suppress E(2)-mediated transcription when overexpressed in estrogen receptor-alpha (ERalpha)-positive cells. Although ERE-BP acts as a competitor for ERE occupancy by liganded ERalpha, the function of IEBP and its human homolog, heat-shock protein 27 (hsp27), is less clear. In data presented here, we have used E(2)-responsive human MCF-7 breast cancer cells to show that IEBP/hsp27 can regulate estrogen signaling as a cytosolic decoy for E(2) and as a protein chaperone for ERalpha. Furthermore, co-immunoprecipitation, colocalization, yeast two-hybrid, and glutathione S-transferase pull-down analyses indicate that IEBP/hsp27 also interacts with ERE-BP to form a dynamic complex that appears to cycle between the cytoplasm and nucleus during normal estrogen signaling. Overexpression of either IEBP/hsp27 or ERE-BP in MCF-7 cells resulted in abnormal subcellular distribution of the IEBP/hsp27 and ERE-BP, with concomitant dysregulation of ERE occupancy as determined by chromatin immunoprecipitation. We hypothesize that IEBP/hsp27 and ERE-BP not only cause hormone resistance in New World primates but are also crucial to normal estrogen signaling in human cells. This appears to involve a physical association between the two proteins to form a complex that is able to interact with both E(2) and ERalpha in cytosolic and nuclear compartments.