Concentrations Of Retinoic Acid Research Articles

Postnatal loss of Cyp26a1 and Cyp26b1 in mice causes impaired retinoid homeostasis in multiple organs

Retinoic acid (RA), the active metabolite of vitamin A (retinol), is essential to various biological processes such as maintenance of epithelia and regulation of cell division, proliferation and differentiation. Cyp26a1 and Cyp26b1 enzymes catalyze hydroxylation of RA and are believed to be responsible for RA clearance in all chordates. Global knockout of either Cyp26a1 or Cyp26b1 is embryonic lethal, demonstrating a critical role of Cyp26 enzymes in regulating RA signaling during fetal development. However, whether Cyp26 activity is required in postnatal life to maintain vitamin A homeostasis is still not clear. We hypothesized that postnatal loss of Cyp26a1 and Cyp26b1 would decrease RA clearance, and consequently alter tissue retinoid concentrations and cause retinoid toxicity. A tamoxifen‐inducible Cre‐loxP system was used to induce a conditional global knockout of Cyp26a1 and Cyp26b1 (double‐knockout; DKO). The knock‐out was induced in female and male mice with tamoxifen injections at 21 days postpartum and then these animals were monitored (body weight and condition) biweekly for 8 weeks. Animals were euthanized if they received a body condition score ≤ 2 or had lost > 15% of their pre‐tamoxifen injection body weight. Tissues were harvested for histological analysis and retinoid measurements. All WT animals were healthy and euthanized after the 8‐week follow‐up but 45% of male and 41% of female DKO animals were euthanized before the completion of the 8‐week follow‐up according to the criteria described above. Compared to WT mice, DKO animals showed significant decrease in weight gain. DKO mice had moderate to severe blepharitis and dermatitis with skin thickening and inflammation. Spleens of DKO mice were significantly enlarged and showed extramedullary hematopoiesis. Cell proliferation in the epidermis and in the epithelium of nonglandular stomach was increased in DKO animals. In general, retinoid homeostasis was altered in DKO animals. In comparison to WT animals, skin, spleen and liver RA concentrations were significantly increased in DKO mice while tissue retinol and retinyl ester concentrations were unchanged. In contrast, serum retinol and retinol binding protein 4 (RBP4) concentrations were significantly decreased in DKO mice with no change in RA concentrations. When DKO animals were dosed with exogenous RA (1mg/kg; i.p.), animals showed signs of toxicity and the exposure to RA was significantly greater in DKO animals than in WT animals. Collectively these data show that Cyp26a1 and Cyp26b1 are required for maintaining vitamin A homeostasis and retinoid signaling also in postnatal life.

Vitamin A regulates neural stem cell proliferation in rats after hypoxic-ischemic brain damage via RARɑ-mediated modulation of the β-catenin pathway

Our previous experiments found that a suitable dose of vitamin A (VA) can affect neuronal apoptosis after hypoxic-ischemic brain damage (HIBD) by binding to RARα to activate the PI3K/AKT signaling pathway; however, the other neuroprotective effects of VA after HIBD, for example, whether it promotes neural stem cell (NSC) proliferation, remain unclear. In this study, in vivo and in vitro experiments revealed that VA regulates β-catenin signaling through RARɑ to affect NSC proliferation after HIBD and to improve neurocognitive outcomes. Because of the accumulation and suspended growth characteristics of NSCs, we performed in vitro experiments with PC12 cells to mimic NSCs. Flow cytometry, CCK8, EdU staining, immunofluorescence and behavioral tests were performed to explore the effects of retinoic acid (RA) on NSC proliferation and post-HIBD function. The expression of RARα and β-catenin pathway components were measured by real-time PCR and Western blotting. We found that the learning and memory of the VA-deficient (VAD) group was more seriously damaged than that of the VA normal (VAN) group. The proliferation of hippocampal NSCs was significantly decreased in the VAD group compared with the VAN group. The mRNA and protein expression of RARɑ, AKT, GSK-3β, β-catenin and Cyclin D1 were significantly lower in the VAD group than in the VAN group. In vitro, too high and too low of an RA intervention resulted in decreased proliferation, while an appropriate RA concentration (1−5 μmol/L) significantly promoted proliferation, S phase cells and high β-catenin pathway expression. These results suggested that VA can exert a neuroprotective effect by promoting the proliferation of hippocampal NSCs after neonatal HIBD injury at the appropriate concentration. VA activates RARɑ, which regulates the β-catenin signaling pathway, which in turn upregulates Cyclin D1 expression, promotes NSC proliferation, and finally plays a role in the neuroprotective effect.

Inhibition of GSK3 Represses the Expression of Retinoic Acid Synthetic Enzyme ALDH1A2 via Wnt/β-Catenin Signaling in WiT49 Cells.

Organogenesis, including renal development, requires an appropriate retinoic acid concentration, which is established by differential expression of aldehyde dehydrogenase 1 family member A2 (ALDH1A2) and cytochrome P450 family 26 subfamily A/B/C member 1 (CYP26A1/B1/C1). In the fetal kidney, ALDH1A2 expresses in the developing stroma and renal vesicle and its derivatives but does not present in the ureteric bud. It remains unclear what may contribute to this expression pattern. Here we show that the glycogen synthase kinase 3 alpha/beta (GSK3A/B) inhibitor CHIR99021 significantly represses ALDH1A2 expression in WiT49, which is a Wilms’ tumor cell line that exhibits “triphasic” differential potential and is used as a fetal kidney cell model. CHIR99021 fails to suppress ALDH1A2 as β-catenin is inhibited, suggesting that the downregulation of ALDH1A2 by CHIR99021 is through Wnt/β-catenin signaling. Ectopic expression of mouse Wnt1, Wnt3a, Wnt4, and Wnt9b represses ALDH1A2 expression in WiT49 cells. Using immunohistochemistry, we show an inverse correlation of Aldh1a2 expression with β-catenin in rat E18.5 kidney. ChIP demonstrated that β-catenin is recruited to the ALDH1A2 promoter, the conserved intron1G, and another site within intron 1 of ALDH1A2. Using a luciferase assay, we further show that the ALDH1A2 promoter and the intron1G element are involved in the repression of ALDH1A2 expression by CHIR99021. Our work demonstrates that ALDH1A2 expression can be directly repressed by the Wnt/β-catenin signaling in fetal kidney cells, suggesting that Wnt/β-catenin may play a role in maintaining the expression pattern of ALDH1A2 in the fetal kidney, thus controlling the availability and localization of retinoic acid and regulating aspects of kidney development.

Retinoic Acids in the Treatment of Most Lethal Solid Cancers.

Although the use of oral administration of pharmacological all-trans retinoic acid (ATRA) concentration in acute promyelocytic leukaemia (APL) patients was approved for over 20 years and used as standard therapy still to date, the same use in solid cancers is still controversial. In the present review the literature about the top five lethal solid cancers (lung, stomach, liver, breast, and colon cancer), as defined by The Global Cancer Observatory of World Health Organization, and retinoic acids (ATRA, 9-cis retinoic acid, and 13-cis retinoic acid, RA) was compared. The action of retinoic acids in inhibiting the cell proliferation was found in several cell pathways and compartments: from membrane and cytoplasmic signaling, to metabolic enzymes, to gene expression. However, in parallel in the most aggressive phenotypes several escape routes have evolved conferring retinoic acids-resistance. The comparison between different solid cancer types pointed out that for some cancer types several information are still lacking. Moreover, even though some pathways and escape routes are the same between the cancer types, sometimes they can differently respond to retinoic acid therapy, so that generalization cannot be made. Further studies on molecular pathways are needed to perform combinatorial trials that allow overcoming retinoic acids resistance.

Induction de la différenciation neuronale par deux polyphénols présents dans le régime méditerranéen : le resvératrol et l'apigénine

To prevent neurodegeneration associated to aging or observed in numerous neurodegenerative diseases, it can be of interest to favor neuronal differentiation of immature and pluripotent stem cells. ODN, produced by astrocytes, is an endozepine generated through the proteolytic cleavage of the diazepam binding inhibitor (DBI). ODN stimulates neurogenesis in the adult mouse brain and prevents apoptosis associated with oxidative stress. Retinoic acid (RA) triggers the differentiation of numerous cell types, including nerve cells. Apigenin (API), present in parsley, rosemary, and honey, promotes the differentiation of B104 rat neuronal cells. Resveratrol (RSV), a major compound found in red wine, activates neuronal differentiation of human bone marrow mesenchymal stem cells via SIRT1. RA, API and RSV cross the blood brain barrier. In the context of neuroprotection, it is therefore of interest to compare the differentiating capacities and the toxicity of these molecules. The most relevant molecules will be the one strongly inducing differentiation with no cytotoxic side effects. To this end, murine neuronal N2a cells were used and cultured with different concentrations of ODN (10-16M – 10-8M), retinoic acid (RA: 6.25µM-50µM), resveratrol (RSV: 6.25µM-50µM) and API (6.25µM-50µM) for 48 h without or with 10% fetal bovine serum (FBS). Neuronal differentiation was morphologically (presence of dendrites and axons) and cytologically (presence of Nissl bodies) evaluated. Cell viability was determined by staining with fluoresceine diacetate (FDA). The presence of metabolically active axons was evaluated by Mitotracker staining. Neuronal differentiation was much more efficient in the absence of serum (AR (61%) > ODN (37%) ≥ RSV (37%) > API (33%)). At concentrations inducing differentiation, no cytotoxicity was observed for ODN or RSV, API was slightly toxic, RA induces a marked cytotoxicity. For ODN, metabolically active neurons were observed. Thus, polyphenols present in the Mediterranean diet (RSV, API) could contribute to prevent neurodegeneration and are therefore of high interest in regenerative medicine.

Serum Retinoic Acid Level and The Risk of Poststroke Cognitive Impairment in Ischemic Stroke Patients

Background: Retinoic acid (RA), an active metabolite of vitamin A, possesses enormous protective effects on vascular systems. It may also be positively related to good functional outcome after ischemic stroke. However, whether circulating RA concentration is associated with poststroke cognitive impairment (PSCI) remains unclear. This study aimed to detect the association between RA level and PSCI among patients with first-ever acute ischemic stroke. Methods: Two hundred and 61 consecutive patients were prospectively recruited during March 2018 and March 2019. Serum RA concentration was measured at admission for all patients. We also performed cognitive function examination using the Montreal Cognitive Assessment (MoCA) at admission and at every follow-up visit. Patients with MoCA score less than 26 were identified as developing PSCI. Results: The median serum RA level was 2.0 ng/mL (interquartile range, 1.1-3.2 ng/mL) after admission. Patients diagnosed as PSCI at admission, 1-month and 3-month were 53 (20.3%), 91 (34.6%), and 141 (54.0%), respectively. Univariate analysis showed that reduced RA level was correlated with PSCI at 3-month (P = .003), but not at admission (P = .416) and 1-month poststroke (P = .117). After adjusting for all potential confounders, the odds ratio for the lowest tertile of RA, compared with the highest tertile, was 1.97 (95% confidence interval, 1.01-3.83, P = .046) for PSCI at 3 months. Furthermore, multiple-adjusted spline regression model further confirmed the dose-response relationships between RA level and 3-month PSCI (P < .001). Conclusions: Decreasing serum RA level might be associated with 3-month PSCI in ischemic stroke patients.

Self-organized formation of developing appendages from murine pluripotent stem cells

Limb development starts with the formation of limb buds (LBs), which consist of tissues from two different germ layers; the lateral plate mesoderm-derived mesenchyme and ectoderm-derived surface epithelium. Here, we report means for induction of an LB-like mesenchymal/epithelial complex tissues from murine pluripotent stem cells (PSCs) in vitro. The LB-like tissues selectively differentiate into forelimb- or hindlimb-type mesenchymes, depending on a concentration of retinoic acid. Comparative transcriptome analysis reveals that the LB-like tissues show similar gene expression pattern to that seen in LBs. We also show that manipulating BMP signaling enables us to induce a thickened epithelial structure similar to the apical ectodermal ridge. Finally, we demonstrate that the induced tissues can contribute to endogenous digit tissue after transplantation. This PSC technology offers a first step for creating an artificial limb bud in culture and might open the door to inducing other mesenchymal/epithelial complex tissues from PSCs.

Potential for combined delivery of riboflavin and all-trans retinoic acid, from silk fibroin for corneal bioengineering.

Millions of people worldwide suffer from vision impairing conditions resulting from corneal injury or disease. Silk fibroin (SF) is an emerging biopolymer that has been used for several applications including the fabrication of bioengineered corneas and ocular prostheses. To improve the cell response to SF, riboflavin (RF) and all-trans retinoic acid (RA) were coupled onto SF matrices. RF is a photo-initiator that has previously been combined with ultraviolet light to crosslink corneal collagen while RA has been used to regulate the phenotype of corneal stromal cells and their extracellular matrix deposition. Different concentrations of RF and RA were respectively photo-crosslinked and covalently bound through carbodiimide coupling onto 2% SF matrices. The effect of incorporating these molecules on the physical, chemical and mechanical properties of the matrices was evaluated. The biological response of human corneal stromal cells to the matrices was examined using cellular adhesion assays, proliferation assays, cytoskeleton staining, gene expression analysis and immunocytochemical staining. RF and RA both led to changes in the surface nanostructure and hydrophilicity while just RF increased the material stiffness. Cells cultured on the matrices containing both biomolecules displayed improved cellular proliferation, increased GAG deposition and increased expression of keratocyte genes that are normally associated with healthy corneal stromal tissue. These in vitro studies serve as a starting point for the optimization of loading bioactive molecules on SF based matrices for formulating clinically relevant ocular implants.

The Usefulness of Retinoic Acid Supplementation during In Vitro Oocyte Maturation for the In Vitro Embryo Production of Livestock: A Review.

Simple SummaryIn this review, we provide the previous studies, state-of-the-art practices, and potential implications of retinoic acid for improving in vitro livestock embryo production. Retinoic acid (RA) is an indigenous metabolite and descriptive physiologically functioning constituent of vitamin A. Retinoids were documented as vital regulators for cell development and distinction, embryonic growth, and reproductive function in both male and female livestock. Previously, RA has been shown to have several positive impacts in vivo and in vitro and critically control many reproductive events, such as oocyte development, follicular growth, and early embryonic growth. In addition, RA manages apoptotic signaling and oxidative damages in cells. Recently, RA has been used widely in assisted reproductive technology fields, especially during in vitro embryo development in various mammalian species, including buffaloes, bovine, goats, sheep, pigs, and rabbits. However, the optimum concentration of RA greatly differs based on the condition of maturation media and species. Based on the obtained findings, it was generally accepted that RA enhances nuclear oocyte maturation, cleavage and maturation rates, blastocyst formation, and embryo development. As such, it possesses antioxidant properties against reactive oxygen species (ROS) and an anti-apoptotic effect through enhancing the transcription of some related genes such as superoxide dismutase, prostaglandin synthase, glutathione peroxidase, peroxiredoxins, and heme oxygenase. Therefore, the current review concludes that an addition of RA (up to 50 nM) has the potential to improve the oocyte maturation media of various species of livestock due to its antioxidant activity.

Upregulation of amphiregulin by retinoic acid and Wnt signalling promotes liver cancer cell proliferation.

Activated hepatic stellate cells promote hepatocellular carcinoma (HCC) progression. Hepatic stellate cells play a key role in retinoid metabolism, and activation of stellate cells increases retinoic acid (RA) in the liver. However, the role of RA in HCC proliferation remains unclear. We aimed to analyse the mechanism of RA in HCC proliferation. Thirty-eight patients who had undergone hepatic resection for HCCs were recruited. Paired non-tumour tissues, adjacent and distal to HCCs, were collected, and the RA levels in the tissues were analysed. The mechanisms of RA and HCC proliferation were assessed in liver cancer cell lines by protein and gene expression analyses. Early recurrence of HCC was significantly higher in patients with a higher RA concentration than in those with a lower RA concentration in tissues adjacent to HCCs (61.1% vs. 20%, p = .010). RA promoted HCC cell proliferation and activated the expression of Amphiregulin, a growth factor in hepatocarcinogenesis. The promoter of Amphiregulin contained the binding sites of the RA receptor, RXRα. Wnt signalling also activated the expression of Amphiregulin, and the RA and Wnt pathways acted synergistically to increase the expression of Amphiregulin. Furthermore, RXRα interacted with β-catenin and then translocated to the nucleus to activate Amphiregulin. An increased RA concentration in the tissues adjacent to the tumour was associated with an early recurrence of HCC. RA activated the expression of Amphiregulin, and then promoted HCC proliferation, which might partly contribute to early recurrence of HCC after hepatic resection.

Retinoic acid: A potential therapeutic agent for cryptorchidism infertility based on investigation of flutamide-induced cryptorchid rats in vivo and in vitro

Cryptorchidism is a common disorder in children and may cause infertility in adults. The BTB is essential for maintaining the microenvironment necessary for normal spermatogenesis. This study investigated whether retinoic acid (RA) may regulate the proteins that are essential for integrity of the BTB in cryptorchidism. Female Sprague-Dawley rats were administrated flutamide during late pregnancy to induce a model of cryptorchidism in male offspring. The concentrations of RA and BTB tight and gap junction protein levels were significantly lower in untreated cryptorchid pups compared with normal pups, but almost normal in cryptorchid pups given RA. Studies in vitro corroborated these findings. The sperm quality of RA-treated model pups was better compared with the untreated model. RA treatment may have therapeutic potential to restore retinoic acid and proteins associated with integrity of the BTB in cryptorchid testis.

PML–RARα induces all-trans retinoic acid-dependent transcriptional activation through interaction with MED1

ABSTRACTTranscriptional activation by PML–RARα, an acute promyelocytic leukemia-related oncofusion protein, requires pharmacological concentrations of all-trans retinoic acid (ATRA). However, the mechanism by which the liganded PML–RARα complex leads to the formation of the preinitiation complex has been unidentified. Here we demonstrate that the Mediator subunit MED1 plays an important role in the ATRA-dependent activation of the PML–RARα-bound promoter. Luciferase reporter assays showed that PML–RARα induced significant transcription at pharmacological doses (1 μM) of ATRA; however, this was submaximal and equivalent to the level of transcription driven by intact RARα at physiological doses (1 nM) of ATRA. Transcription depended upon the interaction of PML–RARα with the two LxxLL nuclear receptor recognition motifs of MED1, and LxxLL→LxxAA mutations led to minimal transcription. Mechanistically, MED1 interacted ATRA-dependently with the RARα portion of PML–RARα through the two LxxLL motifs of MED1. These results suggest that PML–RARα initiates ATRA-induced transcription through its interaction with MED1.

Undifferentiated spermatogonia regulate Cyp26b1 expression through NOTCH signaling and drive germ cell differentiation.

Cytochrome P450 family 26 subfamily B member 1 (CYP26B1) regulates the concentration of all-trans retinoic acid (RA) and plays a key role in germ cell differentiation by controlling local distribution of RA. The mechanisms regulating Cyp26b1 expression in postnatal Sertoli cells, the main components of the stem cell niche, are so far unknown. During gonad development, expression of Cyp26b1 is maintained by Steroidogenic Factor 1 (SF-1) and Sex-Determining Region Y Box-9 (SOX9), which ensure that RA is degraded and germ cell differentiation is blocked. Here, we show that the NOTCH target Hairy/Enhancer-of-Split Related with YRPW Motif 1 (HEY1), a transcriptional repressor, regulates germ cell differentiation via direct binding to the Cyp26b1 promoter and thus inhibits its expression in Sertoli cells. Further, using in vivo germ cell ablation, we demonstrate that undifferentiated type A spermatogonia are the cells that activate NOTCH signaling in Sertoli cells through their expression of the NOTCH ligand JAGGED-1 (JAG1) at stage VIII of the seminiferous epithelium cycle, therefore mediating germ cell differentiation by a ligand concentration-dependent process. These data therefore provide more insights into the mechanisms of germ cell differentiation after birth and potentially explain the spatiotemporal RA pulses driving the transition between undifferentiated to differentiating spermatogonia.-Parekh, P. A., Garcia, T. X., Waheeb, R., Jain, V., Gandhi, P., Meistrich, M. L., Shetty, G., Hofmann, M.-C. Undifferentiated spermatogonia regulate Cyp26b1 expression through NOTCH signaling and drive germ cell differentiation.

O-GlcNAcylation disrupts STRA6-retinol signals in kidneys of diabetes

BackgroundO-GlcNAcylation is an important mechanism of diabetic complication. Retinoid homeostasis regulates cell-physiological functions through STRA6-retinol signaling. Therefore, we investigated whether O-GlcNAcylation disrupted STRA6-retinol signals in diabetes. MethodsImmunoprecipitation and proximity ligation assay were used to investigate O-GlcNAcylation of STRA6-retinol signals in kidneys of db/db and ob/ob mice. Western blot and immunohistochemistry were done for STRA6/CRBP1/LRAT/RALDH1/RARs pathway, GFAT, OGT, TGFβ1 and collagen 1 level. HPLC and ELISA for retinol, retinal, and retinoic acid concentrations were performed in vivo and vitro. RBP4 binding with STRA6 was measured in vitro. To verify whether O-GlcNAcylation disrupted STRA6-retinol signals, treatment of TMG and OSMI-1, transfection of OGA and OGT, and OGT siRNA were performed in HK-2 cells. ResultsSTRA6 and RALDH1 were highly O-GlcNAc-modified in glomeruli and tubules of db/db and ob/ob mice. RBP4, p-Try, p-JAK2, and p-STAT5 on STRA6 immunoprecipitate were reduced. Cellular retinol signals (CRBP1, LRAT, ADH, retinol, retinal, RA, RARα, RARγ and RXRα) remarkably decreased in kidneys of db/db, ob/ob mice and HG-cultured cells. TMG and OGT transfection induced O-GlcNAcylation of STRA6 and RALDH1, repressed RBP4-bound STRA6, and retinol signals in NG-cultured cells. OSMI-1, OGA transfection, and OGT silence reversed O-GlcNAc-modification of STRA6 and RALDH1, and rescued the decrease of retinol signals, and reversed the increase of TGFβ1 and collagen 1 in HG-treated cells. ConclusionsO-GlcNAcylation significantly modified STRA6 and RALDH1, suppressed RBP4 binding activity, and disrupted retinol signals in the kidney of diabetes. General significanceThis study first indicates that STRA6-retinol signals were directly disrupted by O-GlcNAcylation in diabetic kidney.

ANTICANCER EFFECTS OF RETINOIC ACID IN CERVICAL CANCER CELLS

Cervical cancer is a leading cause of cancer-related death in women, and it is known to have a poor prognosis. This is because, patients develop progressive or recurrent tumours after primary treatment, and the major reason for tumour recurrence is the presence of cancer stem cells (CSCs). It is known that retinoic acid (RA) has potential therapeutic effects on cervical cancer. However, the possible mode of action of RA in cervical cancer cells, and its relation to CSCs remains elusive. The aim of this research was to determine the anticancer effect of RA in cervical cancer cells (HeLa). HeLa cells were treated by various concentrations of RA ranging from 5-50µM to determine the effect of RA on cell viability, and cell proliferation. Both experiments were carried out using Celltiter-glo 2.0 assay and CyQuant NF assay, respectively. Apoptosis activity was determined using Caspase-Glo 3/7 assay. Immunofluorescent staining was conducted to detect the expression of differentiation marker (pan-keratin), and stem cell markers (CD133 and SSEA4) on untreated and treated HeLa cells with 10µM of RA. The findings showed that RA reduced cell viability and proliferation in a dose-dependent manner by 12-83% and 22-86%, respectively. However, a change in caspase3/7 activity between untreated, and 10µM RA-treated Hela cells were not detected indicating absence of apoptotic activity. The study also revealed that expression of differentiation marker (pan-keratin) was up-regulated, while expressions of stem cell markers (CD133 and SSEA4) were down-regulated. In addition, morphology of HeLa cells displayed a more differentiated phenotype that is less proliferative upon RA treatment. These findings suggest that RA showed its anticancer effect on cervical cancer cells by exhibiting cytotoxicity, inhibiting proliferation capacity, and inducing differentiation of cervical cancer cells. This finding shows that retinoic acid may potentially serve as a potent targeted therapy for cervical cancer and other cancers possessing CSCs within its tumors.

Commensals Suppress Intestinal Epithelial Cell Retinoic Acid Synthesis to Regulate Interleukin-22 Activity and Prevent Microbial Dysbiosis

Retinoic acid (RA), a vitamin A metabolite, regulates transcriptional programs that drive protective or pathogenic immune responses in the intestine, in a manner dependent on RA concentration. Vitamin A is obtained from diet and is metabolized by intestinal epithelial cells (IECs), which operate in intimate association with microbes and immune cells. Here we found that commensal bacteria belonging to class Clostridia modulate RA concentration in the gut by suppressing the expression of retinol dehydrogenase 7 (Rdh7) in IECs. Rdh7 expression and associated RA amounts were lower in the intestinal tissue of conventional mice, as compared to germ-free mice. Deletion of Rdh7 in IECs diminished RA signaling in immune cells, reduced the IL-22-dependent antimicrobial response, and enhanced resistance to colonization by Salmonella Typhimurium. Our findings define a regulatory circuit wherein bacterial regulation of IEC-intrinsic RA synthesis protects microbial communities in the gut from excessive immune activity, achieving a balance that prevents colonization by enteric pathogens.

Anti-Leukemic Effect of Retinoic Acid in Non-APL AML Cells

[Background] Differentiation therapy with retinoic acid (RA) has remarkably improved the cure rate for acute promyelocytic leukemia (APL). RAs are known to have anti-leukemic effect in parts of non-APL acute myelocytic leukemia (AML) cells. It has been reported that AML patient with NPM1 or IDH1/2 mutation may have sensitivity to all-trans retinoic acid (ATRA) and the clinical study with combination of chemotherapy and ATRA is conducted in NPM1 mutated AML. In addition, ATRA and a FLT3 inhibitor, quizartinib, showed synergistic activity against FLT3-ITD positive AML patients' samples and their combination therapy improved the survival of AML xenograft mouse model. Moreover, it is also reported that the presence of super-enhancer at RARA gene locus is related to high RARA mRNA expression and sensitivity to tamibarotene. Another study showed that ATRA promote cancer apoptosis in the presence of Cellular Retinoic Acid-Binding Protein 1 (CRABP1) through G1 expansion. However, the efficacy of RAs and its mechanism in non-APL AML are still largely unknown. In this study, we evaluated anti-leukemic effect of RAs on primary AML cells and explored its predictive biomarkers for the purpose of optimization of therapy for non-APL AML.[Method] We examined growth inhibitory and differentiation effects of ATRA and tamibarotene on primary AML cells in vitro. Primary AML cells were purified by density-based centrifugation and cultured with various concentrations of RAs in methylcellulose-based media including cytokines. IC50 values of RAs were calculated by luminescent cell viable assay on day7 and 14. Cell differentiation upon RAs treatment was also examined in these cells by morphology and expression of CD11b using flow cytometry analysis. We also evaluated the efficacy of combination therapy of RAs and several tyrosine kinase inhibitors, quizartinib, midstaurin and dasatinib, and assessed their synergistic effect by calculating combination index. The association of IC50 values of RAs with clinical characteristics, mRNA expressions of RARA and CRABP1, and genetic mutations were investigated.[Result] We analyzed total of 30 primary non-APL AML samples and IC50 values of ATRA and tamibarotene were lower than 5 µM in 14 of 30 (46.7 %) and 4 of 14 (28.6 %) AML cells, respectively. There were no significant difference in IC50 value of ATRA and tamibarotene by FAB subtype and chromosomal abnormalities. ATRA and tamibarotene induced differentiation in 10 of the 22 and 2 of the 9, respectively, and anti-leukemic effect of ATRA and tamibarotene were not associated with these differentiation statuses. IC50 value of ATRA and tamibarotene were significantly lower in ASXL1 (p=0.0071 and p=0.0012, respectively), SRSF2 (p=0.0101 and p=0.0113, respectively), and IDH2 (p=0.0295 and p=0.0044, respectively) mutated AML cells. FLT3-ITD mutation with high allelic ratio (>0.5) was associated with high IC50 value of ATRA (p=0.0116). Although NPM1 mutation was associated with higher IC50 value of ATRA, all of 4 patients with NPM1 mutation concurrently have FLT3-ITD mutations in this study. Other gene mutations were not correlated with RAs sensitivity. The expression of RARA mRNA weakly correlated with sensitivity of ATRA and tamibarotene (P=0.1126 and P=0.0711 respectively), but it was not significant.[Conclusion] RAs were effective in almost half of non-APL AML cells in vitro and some AML cells were sensitive to ATRA without cell differentiation. Mutation in ASXL1, SRSF2, and IDH2 were identified as predictive factors for the RAs sensitivity, whereas the expression of RARA mRNA and other gene mutations were not correlated with RAs sensitivity. [Display omitted] DisclosuresKiyoi:Takeda Pharmaceutical Co., Ltd.: Research Funding; Phizer Japan Inc.: Research Funding; Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; Chugai Pharmaceutical Co., Ltd.: Research Funding; FUJIFILM Corporation: Research Funding; Kyowa Hakko Kirin Co., Ltd.: Research Funding; Sanofi K.K.: Research Funding; Otsuka Pharmaceutical Co., Ltd.: Research Funding; Novartis Pharma K.K.: Research Funding; Zenyaku Kogyo Co., Ltd.: Research Funding; Eisai Co., Ltd.: Research Funding; Bristol-Myers Squibb: Honoraria; Celgene Corporation: Research Funding; Astellas Pharma Inc.: Research Funding; Nippon Shinyaku Co., Ltd.: Research Funding.

Combinational effects of mechanical forces and substrate surface characteristics on esophageal epithelial differentiation.

Even the efficacy of substrate and mechanical stimuli in addition to biochemical cues have been recognized in many studies of stem cell differentiation, few studies have been reported on the differentiation into esophageal epithelial cells. Therefore, the aim of this study was set to propose a method of differentiating stem cells into esophageal epithelial cells according to biochemical reagent concentration, substrate properties, and mechanical forces. After the concentration of all-trans retinoic acid was determined as 5 μM by a baseline experiment, the degree of differentiation was compared in three different kinds of substrates: cover glass, polyurethane (PU) membrane, and electrospun PU sheet (ePU). Then, on the substrate showing the more positive results, that is, ePU, two types of mechanical forces, intermittent hydrostatic pressure (IHP), and shear stress (SS), were applied individually at different magnitudes for the latter 7 days of an overall incubation period of 14 days. Following various biological assays, the lower IHP (50 mmHg) resulted in greater positive effects than the others. Even with cessation of the mechanical force, the relevant markers were remarkably increased. Although the range of factors regulating differentiation was limited, this study nonetheless demonstrated the combinational effects of mechanical force along with substrate type for the first time in related studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 552-560, 2019.

Identification of influential proteins in the classical retinoic acid signaling pathway

BackgroundIn the classical pathway of retinoic acid (RA) mediated gene transcription, RA binds to a nuclear hormone receptor dimer composed of retinoic acid receptor (RAR) and retinoid X receptor (RXR), to induce the expression of its downstream target genes. In addition to nuclear receptors, there are other intracellular RA binding proteins such as cellular retinoic acid binding proteins (CRABP1 and CRABP2) and cytochrome P450 (CYP) enzymes, whose contributions to the RA signaling pathway have not been fully understood. The objective of this study was to compare the significance of various RA binding receptors, i.e. CRABP1, CRABP2, CYP and RAR in the RA signaling pathway. In this regard, we developed a mathematical model of the RA pathway, which is one of the few models, if not the only one, that includes all main intracellular RA binding receptors. We then performed a global sensitivity analysis (GSA) to investigate the contribution of the RA receptors to RA-induced mRNA production, when the cells were treated with a wide range of RA levels, from physiological to pharmacological concentrations.ResultsOur results show that CRABP2 and RAR are the most and the least important proteins, respectively, in controlling the model performance at physiological concentrations of RA (1–10 nM). However, at higher concentrations of RA, CYP and RAR are the most sensitive parameters of the system. Furthermore, we found that depending on the concentrations of all RA binding proteins, the rate of metabolism of RA can either change or remain constant following RA therapy. The cellular levels of CRABP1 are more important than that of CRABP2 in controlling RA metabolite formation at pharmacological conditions (RA = 0.1–1 μM). Finally, our results indicate a significant negative correlation between total mRNA production and total RA metabolite formation at pharmacological levels of RA.ConclusionsOur simulations indicate that the significance of the RA binding proteins in the RA pathway of gene expression strongly depends on intracellular concentration of RA. This study not only can explain why various cell types respond to RA therapy differently, but also can potentially help develop pharmacological methods to increase the efficacy of the drug.

Melatonin Can Strengthen the Effect of Retinoic Acid in HL-60 Cells.

Melatonin is produced by the pineal gland. It can be regarded as an anticancer agent and used for combined therapy, owing to its oncostatic, antioxidant, and immunoregulatory activities. Retinoic acid is widely used for the treatment of acute promyelocytic leukemia; however, it has adverse effects on the human organism. We investigated the effect of melatonin and reduced concentrations of retinoic acid on the activation of proliferation in acute promyelocytic leukemiaon a cell model HL-60. The combined effect of these compounds leads to a reduction in the number of cells by 70% and the index of mitotic activity by 64%. Combined treatment with melatonin and retinoic acid decreased the expression of the Bcl-2. The mitochondrial isoform VDAC1 can be a target in the treatment of different tumors. The combined effect of and retinoic acid at a low concentration (10 nM) decreased VDAC1 expression. Melatonin in combination with retinoic acid produced a similar effect on the expression of the translocator protein. The coprecipitation of VDAC with 2′,3′-cyclonucleotide-3′-phosphodiesterase implies a possible role of its in cancer development. The combined effect of retinoic acid and melatonin decreased the activity of the electron transport chain complexes. The changes in the activation of proliferation in HL-60 cells, the mitotic index, and Bcl-2 expression under combined effect of retinoic acid (10 nM) with melatonin (1 mM) are similar to changes that are induced by 1 μM retinoic acid. Our results suggest that MEL is able to improve the action the other chemotherapeutic agent.